From The Paul Scherrer Institute [Paul Scherrer Institut](CH): “New materials for the computer of the future”

From The Paul Scherrer Institute [Paul Scherrer Institut](CH)

12.8.22
Written by Bernd Müller

Contact
Prof. Dr. Milan Radovic
Synchrotron Light Source SLS
Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
+41 56 310 55 65
milan.radovic@psi.ch

Milan Radovic is a staff scientist at the Spectroscopy of Interfaces and Surfaces (SIS) Beam Line, Swiss Light Source. He studied Applied Physics at the University of Belgrade, Serbia, where he also started his research career at the Department of Atomic Physics. In 2009 he obtained his PhD from the University of Naples, Italy. In 2003 he was invited to take up a dual appointment with EPFL Lausanne and PSI, where he has been a staff scientist since 2013. (Photo: Paul Scherrer Institute/Mahir Dzambegovic)

Milan Radovic and Eduardo Bonini Guedes from the Spectroscopy of Quantum Materials Group at the SIS beamline of the Swiss Light Source. (Photo: Paul Scherrer Institute/Mahir Dzambegovic)

Surface and bulk electronic structure of La-doped BaSnO3. a Valence band dispersion parallel to Γ-X, acquired with incoming photon energies of 80, 122, and 132 eV, corresponding to different perpendicular momentum kz values as indicated by the white curves in (b). The measured band structure is overlaid with the LQSGW band structure calculated for bulk BaSnO3. The measured and calculated bands show good agreement, with a clear dispersion along kz. b Intensity map at the Fermi energy in the plane perpendicular to the sample surface (kx–kz), measured with incoming photon energies ranging from 20 to 145 eV. No clear periodicity is evident along kz. The black squares indicate the Brillouin zone boundaries as inferred by the periodicity of the valence bands shown in panel (a), using the LQSGW calculations as a reference. The red circumferences mark the expected bulk Fermi surface centered at the Γ points (c) Sketch illustrating the difference between the measured and calculated Fermi surfaces. The calculated 3D sphere-like Fermi surface with Fermi momentum kF based on the nominal doping of the film is shown in red, while the measured 2D cylinder-like Fermi surface with kF based on the measurements results is shown in green. ARPES intensity follows the attached color scale bar. Credit: Communications Physics (2022).

Novel materials could revolutionize computer technology. Research conducted by scientists at the Paul Scherrer Institute PSI using the Swiss Light Source [below] has reached an important milestone along this path.

Microchips are made from silicon and work on the physical principle of a semiconductor. Nothing has changed here since the first transistor was invented in 1947 in the Bell Labs in America. Ever since, researchers have repeatedly foretold the end of the silicon era – but have always been wrong. Silicon technology is very much alive, and continues to develop at a rapid pace. The IT giant IBM has just announced the first microprocessor whose transistor structures only measure two nanometres, equivalent to 20 adjacent atoms. So what’s next? Even tinier structures? Presumably so – for this decade, at least.

At the same time, new ideas are taking shape in research laboratories regarding a revolutionary technology that could turn everything we think we know about microelectronics on its head. One of the shining lights in this research field is given by Milan Radovic team. Milan Radovic works at the Paul Scherrer Institute and his team just published an article in the journal Communication Physics [below] presenting sensational findings from cutting-edge research into transparent oxides (TOs) that could open up huge prospects for this novel technology.

Innovative microchips

Radovic and his co-authors Muntaser Naamneh and Eduardo Guedes, together with the Bharat Jalan research group from the University of Minnesota, do not work with silicon, but with transition metal oxides (TMOs). These exhibit exotic properties and multifunctional phenomena such as high-temperature superconductivity, colossal magnetoresistance, metal-insulator transition and much more besides. What may initially sound bewildering to a lay person promises enormous advances for the chip technology of the future.

In their latest publication [below], the researchers focus on barium tin oxide (BaSnO3), a material that combines optical transparency with high electrical conductivity.

Scientists have been trying for some time to elicit semiconductor-like properties from transition metals as well as special transparent oxides such as BaSnO3 and strontium stannate (SrSnO3). Compared with silicon, they offer ground-breaking advantages for optoelectronic elements: these transparent, conductive perovskite oxides, would make it possible to create switching elements with directly linked electrical and optical properties. It may then be conceivable to produce transistors that can be switched with light.

Knowledge of interfaces is critical

All microchips are made from a combination of different substances. To understand their function, it is important to know what happens in the thin adjacent layers, or interfaces, between these materials, because the physical properties of many materials are completely different on the surface compared with their interior. “Exotic phases” can occur at the interfaces of materials – a discovery made by three British physicists who were awarded the Nobel Prize in 2016. The article just published describes significant advances in the understanding of the surface-state electronic properties of BaSnO3.

The researchers used angle-resolved photoemission spectroscopy at the beamline of the Swiss Light Source SLS to “discover the two-dimensional electronic state of BaSnO3 , which opens up new prospects for this class of materials,” stresses Eduardo Guedes.

Optimal facilities for spectroscopy at the SLS

It is no coincidence that these findings were made at PSI: researchers on the PSI campus have access to a laboratory specialising in designing, producing, modifying and thoroughly investigating new materials. In addition, the SLS at PSI offers the very best facilities for screening substances at high spatial and temporal resolution. These sophisticated spectroscopy methods are a speciality of PSI, Switzerland’s foremost research centre. There are only three locations worldwide that simultaneously meet all these requirements. The relevant know-how and advanced research infrastructure are also important prerequisites. “At PSI we explore and combine a knowledge with experimental facilities,” says Radovic. Now the researchers want to find out which other materials exhibit similar properties and could be potential candidates for the optical microchips of the future.

But silicon is far from being an outdated technology, Milan Radovic stresses. It is in fact highly developed and efficient. “However, technology based on transition metal oxides is much more powerful and versatile – its time will come.”

Science paper:
Communication Physics
See the science paper for instructive material with images.

See the full article here.

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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Please help promote STEM in your local schools.

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Paul Sherrer Institute SwissFEL Coherent Light Source, Spallation Neutron Source (SINQ), Muon Source (SμS), X-ray free-electron laser (SwissFEL).

The Paul Scherrer Institute [Paul Scherrer Institut] (CH) is the largest research institute for natural and engineering sciences within Switzerland. We perform world-class research in three main subject areas: Matter and Material; Energy and the Environment; and Human Health. By conducting fundamental and applied research, we work on long-term solutions for major challenges facing society, industry and science.

The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the River Aare, and covers an area over 35 hectares in size. Like ETH Zurich [Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH) and EPFL [Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH)], PSI belongs to the Swiss Federal Institutes of Technology Domain of the Swiss Confederation . The PSI employs around 2100 people. It conducts basic and applied research in the fields of matter and materials, human health, and energy and the environment. About 37% of PSI’s research activities focus on material sciences, 24% on life sciences, 19% on general energy, 11% on nuclear energy and safety, and 9% on particle physics.
PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1900 experiments are conducted each year at the approximately 40 measuring stations in these facilities.

In recent years, the institute has been one of the largest recipients of money from the Swiss lottery fund.

Research and specialist areas

Paul Scherrer Institute develops, builds and operates several accelerator facilities, e. g. a 590 MeV high-current cyclotron, which in normal operation supplies a beam current of about 2.2 mA. PSI also operates four large-scale research facilities: a synchrotron light source (SLS), which is particularly brilliant and stable, a spallation neutron source (SINQ), a muon source (SμS) and an X-ray free-electron laser (SwissFEL).

This makes PSI currently (2020) the only institute in the world to provide the four most important probes for researching the structure and dynamics of condensed matter (neutrons, muons and synchrotron radiation) on a campus for the international user community. In addition, HIPA’s target facilities also produce pions that feed the muon source and the Ultracold Neutron source UCN produces very slow, ultracold neutrons. All these particle types are used for research in particle physics.

From The Paul Scherrer Institute [Paul Scherrer Institut](CH) And The Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich] (CH) : “Making sense of the muon’s misdemeanours”

From The Paul Scherrer Institute [Paul Scherrer Institut](CH)

And

The Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich] (CH)

11.28.22
Contacts:

Dr. Thomas Prokscha
Low Energy Muons Group Head
Paul Scherrer Institut
Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 42 75
E-Mail: thomas.prokscha@psi.ch

Prof. Dr. Paolo Crivelli
Institute for Particle Physics and Astrophysics
Department of Physics
ETH Zurich
HPT E 7.2, Auguste-​Piccard-Hof 1, 8093 Zürich, Switzerland
Telephone: +41 44 633 35 11
E-Mail: crivelli@phys.ethz.ch

Text: Miriam Arrell/Paul Scherrer Institute

By making precise measurements in muonium, Crivelli and Prokscha are aiming to understand puzzling results using muons, which may in turn reveal gaps in the laws of physics as we know them. (Photo: Paul Scherrer Institute / Mahir Dzambegovic)

By studying an exotic atom called muonium, researchers are hoping misbehaving muons will spill the beans on the Standard Model of particle physics.

Standard Model of Particle Physics, Quantum Diaries.

To make muonium, they use the most intense continuous beam of low energy muons in the world at Paul Scherrer Institute PSI. The research is published in Nature Communications [below].

The muon is often described as the electron’s heavy cousin. A more appropriate description might be its rogue relation. Since its discovery triggered the words “who ordered that” (Isidor Isaac Rabi, Nobel laureate), the muon has been bamboozling scientists with its law-breaking antics. The muon’s most famous misdemeanour is to wobble slightly too much in a magnetic field: its anomalous magnetic moment hit the headlines with the 2021 muon g-2 experiment at Fermilab.

DOE’s Fermi National Accelerator Laboratory Muon g-2 studio. As muons race around a ring at the Muon g-2 studio, their spin axes twirl, reflecting the influence of unseen particles.

The muon also notably caused trouble when it was used to measure the radius of the proton – giving rise to a wildly different value to previous measurements and what became known as the proton radius puzzle. Yet rather than being chastized, the muon is cherished for its surprising behavior, which makes it a likely candidate to reveal new physics beyond the Standard Model. 

Aiming to make sense of the muon’s strange behaviour, researchers from PSI and ETH Zürich turned to an exotic atom known as muonium. Formed from a positive muon orbited by an electron, muonium is similar to hydrogen but much simpler. Whereas hydrogen’s proton is made up of quarks, muonium’s positive muon has no substructure. And this means it provides a very clean model system from which to sort these problems out: for example, by obtaining extremely precise values of fundamental constants such as the mass of the muon.

“With muonium, because we can measure its properties so precisely, we can try to detect any deviation from the Standard Model. And if we see this, we can then infer which of the theories that go beyond the Standard Model are viable or not,” explains Paolo Crivelli from ETH Zürich, who is leading the study supported by a European Research Council Consolidator grant in the frame of the Mu-MASS project.

Only one place in the world this is possible

A major challenge to making these measurements very precisely is having an intense beam of muonium particles so that statistical errors can be reduced. Making lots of muonium, which incidentally lasts for only two microseconds, is not simple. There is one place in the world where enough positive muons at low energy are available to create this: PSI’s Swiss Muon Source.

“To make muonium efficiently, we need to use slow muons. When they’re first produced they’re going at a quarter of the speed of light. We then need to slow them down by a factor of a thousand without losing them. At PSI, we’ve perfected this art. We have the most intense continuous source of low energy muons in the world. So we’re uniquely positioned to perform these measurements,” says Thomas Prokscha, who heads the Low Energy Muons group at PSI.

At the Low Energy Muons beamline, slow muons pass through a thin foil target where they pick up electrons to form muonium. As they emerge, Crivelli’s team are waiting to probe their properties using microwave and laser spectroscopy.

Tiny change in energy levels could hold the key

The property of muonium that the researchers are able to study in such detail is its energy levels. In the recent publication, the teams were able to measure for the first time a transition between certain very specific energy sublevels in muonium. Isolated from other so-called hyperfine levels, the transition can be modeled extremely cleanly. The ability to now measure it will facilitate other precision measurements: in particular, to obtain an improved value of an important quantity known as the Lamb shift.

The Lamb shift is a miniscule change in certain energy levels in hydrogen relative to where they ‘should’ be as predicted by classical theory. The shift was explained with the advent of Quantum Electrodynamics (the quantum theory of how light and matter interact). Yet, as discussed, in hydrogen, protons – possessing substructure – complicate things. An ultra-precise Lamb shift measured in muonium could put the theory of Quantum Electrodynamics to the test.

There is more. The muon is nine times lighter than the proton. This means that effects relating to the nuclear mass, such as how a particle recoils after absorbing a photon of light, are enhanced. Indetectable in hydrogen, a route to these values at high precision in muonium could enable scientists to test certain theories that would explain the muon g-2 anomaly: for example, the existence of new particles such as scalar or vector gauge bosons.

Putting the muon on the scales

However exciting the potential of this may be, the team have a greater goal in their sights: weighing the muon. To do this, they will measure a different transition in muonium to a precision one thousand times greater than ever before.

An ultra-high precision value of the muon mass – the goal is 1 part per billion – will support ongoing efforts to reduce uncertainty even further for muon g-2. “The muon mass is a fundamental parameter that we cannot predict with theory, and so as experimental precision improves, we desperately need an improved value of the muon mass as an input for the calculations,” explains Crivelli.

The measurement could also lead to a new value of the Rydberg constant – an important fundamental constant in atomic physics – that is independent of hydrogen spectroscopy. This could explain discrepancies between measurements that gave rise to the proton radius puzzle, and maybe even solve it once and for all.

Muonium spectroscopy poised to fly with IMPACT project

Given that the main limitation for such experiments is producing enough muonium to reduce statistical errors, the outlook for this research at PSI looks bright. “With the high intensity muon beams proposed for the IMPACT [Isotope and Muon Production using Advanced Cyclotron and Target technologies] project we could potentially go a factor of one hundred higher in precision, and this would be getting very interesting for the Standard Model,” emphasises Prokscha.

Science paper:
Nature Communications
See the science paper for instructive material with images.

See the full article here.

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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Please help promote STEM in your local schools.

Stem Education Coalition

The Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich] (CH) is a public research university in the city of Zürich, Switzerland. Founded by the Swiss Federal Government in 1854 with the stated mission to educate engineers and scientists, the school focuses exclusively on science, technology, engineering and mathematics. Like its sister institution The Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne](CH) , it is part of The Swiss Federal Institutes of Technology Domain (ETH Domain)) , part of the The Swiss Federal Department of Economic Affairs, Education and Research [EAER][Eidgenössisches Departement für Wirtschaft, Bildung und Forschung] [Département fédéral de l’économie, de la formation et de la recherche] (CH).

The university is an attractive destination for international students thanks to low tuition fees of 809 CHF per semester, PhD and graduate salaries that are amongst the world’s highest, and a world-class reputation in academia and industry. There are currently 22,200 students from over 120 countries, of which 4,180 are pursuing doctoral degrees. In the 2021 edition of the QS World University Rankings ETH Zürich is ranked 6th in the world and 8th by the Times Higher Education World Rankings 2020. In the 2020 QS World University Rankings by subject it is ranked 4th in the world for engineering and technology (2nd in Europe) and 1st for earth & marine science.

As of November 2019, 21 Nobel laureates, 2 Fields Medalists, 2 Pritzker Prize winners, and 1 Turing Award winner have been affiliated with the Institute, including Albert Einstein. Other notable alumni include John von Neumann and Santiago Calatrava. It is a founding member of the IDEA League and the International Alliance of Research Universities (IARU) and a member of the CESAER network.

ETH Zürich was founded on 7 February 1854 by the Swiss Confederation and began giving its first lectures on 16 October 1855 as a polytechnic institute (eidgenössische polytechnische schule) at various sites throughout the city of Zurich. It was initially composed of six faculties: architecture, civil engineering, mechanical engineering, chemistry, forestry, and an integrated department for the fields of mathematics, natural sciences, literature, and social and political sciences.

It is locally still known as Polytechnikum, or simply as Poly, derived from the original name eidgenössische polytechnische schule, which translates to “federal polytechnic school”.

ETH Zürich is a federal institute (i.e., under direct administration by the Swiss government), whereas The University of Zürich [Universität Zürich ] (CH) is a cantonal institution. The decision for a new federal university was heavily disputed at the time; the liberals pressed for a “federal university”, while the conservative forces wanted all universities to remain under cantonal control, worried that the liberals would gain more political power than they already had. In the beginning, both universities were co-located in the buildings of the University of Zürich.

From 1905 to 1908, under the presidency of Jérôme Franel, the course program of ETH Zürich was restructured to that of a real university and ETH Zürich was granted the right to award doctorates. In 1909 the first doctorates were awarded. In 1911, it was given its current name, Eidgenössische Technische Hochschule. In 1924, another reorganization structured the university in 12 departments. However, it now has 16 departments.

ETH Zürich, EPFL (Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH), and four associated research institutes form The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) with the aim of collaborating on scientific projects.

Reputation and ranking

ETH Zürich is ranked among the top universities in the world. Typically, popular rankings place the institution as the best university in continental Europe and ETH Zürich is consistently ranked among the top 1-5 universities in Europe, and among the top 3-10 best universities of the world.

Historically, ETH Zürich has achieved its reputation particularly in the fields of chemistry, mathematics and physics. There are 32 Nobel laureates who are associated with ETH Zürich, the most recent of whom is Richard F. Heck, awarded the Nobel Prize in chemistry in 2010. Albert Einstein is perhaps its most famous alumnus.

In 2018, the QS World University Rankings placed ETH Zürich at 7th overall in the world. In 2015, ETH Zürich was ranked 5th in the world in Engineering, Science and Technology, just behind the Massachusetts Institute of Technology, Stanford University and University of Cambridge (UK). In 2015, ETH Zürich also ranked 6th in the world in Natural Sciences, and in 2016 ranked 1st in the world for Earth & Marine Sciences for the second consecutive year.

In 2016, Times Higher Education World University Rankings ranked ETH Zürich 9th overall in the world and 8th in the world in the field of Engineering & Technology, just behind the Massachusetts Institute of Technology, Stanford University, California Institute of Technology, Princeton University, University of Cambridge(UK), Imperial College London(UK) and University of Oxford(UK) .

In a comparison of Swiss universities by swissUP Ranking and in rankings published by CHE comparing the universities of German-speaking countries, ETH Zürich traditionally is ranked first in natural sciences, computer science and engineering sciences.

In the survey CHE Excellence Ranking on the quality of Western European graduate school programs in the fields of biology, chemistry, physics and mathematics, ETH Zürich was assessed as one of the three institutions to have excellent programs in all the considered fields, the other two being Imperial College London (UK) and the University of Cambridge (UK), respectively.

Paul Sherrer Institute SwissFEL Coherent Light Source, Spallation Neutron Source (SINQ), Muon Source (SμS), X-ray free-electron laser (SwissFEL).

The Paul Scherrer Institute [Paul Scherrer Institut] (CH) is the largest research institute for natural and engineering sciences within Switzerland. We perform world-class research in three main subject areas: Matter and Material; Energy and the Environment; and Human Health. By conducting fundamental and applied research, we work on long-term solutions for major challenges facing society, industry and science.

The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the River Aare, and covers an area over 35 hectares in size. Like ETH Zurich [Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH) and EPFL [Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH)], PSI belongs to the Swiss Federal Institutes of Technology Domain of the Swiss Confederation . The PSI employs around 2100 people. It conducts basic and applied research in the fields of matter and materials, human health, and energy and the environment. About 37% of PSI’s research activities focus on material sciences, 24% on life sciences, 19% on general energy, 11% on nuclear energy and safety, and 9% on particle physics.
PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1900 experiments are conducted each year at the approximately 40 measuring stations in these facilities.

In recent years, the institute has been one of the largest recipients of money from the Swiss lottery fund.

Research and specialist areas

Paul Scherrer Institute develops, builds and operates several accelerator facilities, e. g. a 590 MeV high-current cyclotron, which in normal operation supplies a beam current of about 2.2 mA. PSI also operates four large-scale research facilities: a synchrotron light source (SLS), which is particularly brilliant and stable, a spallation neutron source (SINQ), a muon source (SμS) and an X-ray free-electron laser (SwissFEL).

This makes PSI currently (2020) the only institute in the world to provide the four most important probes for researching the structure and dynamics of condensed matter (neutrons, muons and synchrotron radiation) on a campus for the international user community. In addition, HIPA’s target facilities also produce pions that feed the muon source and the Ultracold Neutron source UCN produces very slow, ultracold neutrons. All these particle types are used for research in particle physics.

From The Paul Scherrer Institute [Paul Scherrer Institut](CH): “Nanomaterial from the Middle Ages”

From The Paul Scherrer Institute [Paul Scherrer Institut](CH)

10.10.22
Barbara Vonarburg

To gild sculptures in the late Middle Ages, artists often applied ultra-thin gold foil supported by a silver base layer. For the first time, scientists at the Paul Scherrer Institute PSI have managed to produce nanoscale 3D images of this material, known as “Zwischgold”. The pictures show this was a highly sophisticated mediaeval production technique and demonstrate why restoring such precious gilded artefacts is so difficult.

PXCT 3D images of the 35-year old Zwischgold sample showing the addition of (a) Au, (b) Ag (with transparent voids), (c) “silver corrosion products”, and (d) other segments. (e) Stack plot of the depth profile of the single-layered section of the sample, aligned to the main layer of the Au segment. Credit: Nanoscale (2022).

The samples examined at the Swiss Light Source SLS using one of the most advanced microscopy methods were unusual even for the highly experienced PSI team: minute samples of materials taken from an altar and wooden statues originating from the fifteenth century.

The altar examined is thought to have been made around 1420 in Southern Germany and for a long time stood in a mountain chapel on Alp Leiggern in the Swiss canton of Valais. Today it is on display at the Swiss National Museum (Landesmuseum Zürich). (Photo: Swiss National Museum, Landesmuseum Zürich)

Paul Sherrer Institute SwissFEL Coherent Light Source

The altar is thought to have been made around 1420 in Southern Germany and stood for a long time in a mountain chapel on Alp Leiggern in the Swiss canton of Valais. Today it is on display at the Swiss National Museum (Landesmuseum Zürich). In the middle you can see Mary cradling Baby Jesus. The material sample was taken from a fold in the Virgin Mary’s robe. The tiny samples from the other two medieval structures were supplied by Basel Historical Museum.

The material was used to gild the sacred figures. It is not actually gold leaf, but a special double-sided foil of gold and silver where the gold can be ultra-thin because it is supported by the silver base. This material, known as “Zwischgold” (part-gold) was significantly cheaper than using pure gold leaf. “Although “Zwischgold” was frequently used in the Middle Ages, very little was known about this material up to now,” says PSI physicist Benjamin Watts: “So we wanted to investigate the samples using 3D technology which can visualize extremely fine details.” Although other microscopy techniques had been used previously to examine “Zwischgold”, they only provided a 2D cross-section through the material. In other words, it was only possible to view the surface of the cut segment, rather than looking inside the material. The scientists were also worried that cutting through it may have changed the structure of the sample. The advanced microscopy imaging method used today, “ptychographic tomography”, provides a 3D image of Zwischgold’s exact composition for the first time.

Qing Wu and Benjamin Watts at the cSAXS beamline, where they conducted their investigations. Wu is holding a plate displaying (from top to bottom) one segment each of leaf gold, Zwischgold and silver. The dark patches are formed by oxidised silver. (Photo: Paul Scherrer Institute/Mahir Dzambegovic)

X-rays generate a diffraction pattern

The PSI scientists conducted their research using X-rays produced by the Swiss Light Source SLS [above]. These produce tomographs displaying details in the nanoscale range – millionths of a millimetre, in other words. “’Ptychography’ is a fairly sophisticated method, as there is no objective lens that forms an image directly on the detector,” Watts explains. “Ptychography” actually produces a diffraction pattern of the illuminated area, in other words an image with points of differing intensity. By manipulating the sample in a precisely defined manner it is possible to generate hundreds of overlapping diffraction patterns. “We can then combine these diffraction patterns like a sort of giant Sudoku puzzle and work out what the original image looked like,” says the physicist. A set of “ptychographic” images taken from different directions can be combined to create a 3D “tomogram”.

The advantage of this method is its extremely high resolution. “We knew the thickness of the “Zwischgold” sample taken from Mary was of the order of hundreds of nanometres,” Watts explains. “So we had to be able to reveal even tinier details.” The scientists achieved this using “ptychographic tomography”, as they report in their latest article in the journal Nanoscale [below]. “The 3D images clearly show how thinly and evenly the gold layer is over the silver base layer,” says Qing Wu, lead author of the publication. The art historian and conservation scientist completed her PhD at the University of Zürich, in collaboration with PSI and the Swiss National Museum. “Many people had assumed that technology in the Middle Ages was not particularly advanced,” Wu comments. “On the contrary: this was not the Dark Ages, but a period when metallurgy and gilding techniques were incredibly well developed.”

Secret recipe revealed

Unfortunately there are no records of how “Zwischgold” was produced at the time. “We reckon the artisans kept their recipe secret,” says Wu. Based on nanoscale images and documents from later epochs, however, the art historian now knows the method used in the 15th century: first the gold and the silver were hammered separately to produce thin foils, whereby the gold film had to be much thinner than the silver. Then the two metal foils were worked on together. Wu describes the process: “This required special beating tools and pouches with various inserts made of different materials into which the foils were inserted,” Wu explains. This was a fairly complicated procedure that required highly skilled specialists.

“Our investigations of “Zwischgold” samples showed the average thickness of the gold layer to be around 30 nanometres, while gold leaf produced in the same period and region was approximately 140 nanometres thick,” Wu explains. “This method saved on gold, which was much more expensive”. At the same time, there was also a very strict hierarchy of materials: gold leaf was used to make the halo of one figure, for example, while “Zwischgold” was used for the robe. Because this material has less of a sheen, the artists often used it to colour the hair or beards of their statues. “It is incredible how someone with only hand tools was able to craft such nanoscale material,” Watts says. Mediaeval artisans also benefited from a unique property of gold and silver crystals when pressed together: their morphology is preserved across the entire metal film. “A lucky coincidence of nature that ensures this technique works,” says the physicist.

Golden surface turns black

The 3D images do bring to light one drawback of using “Zwischgold”, however: the silver can push through the gold layer and cover it. The silver moves surprisingly quickly – even at room temperature. Within days, a thin silver coating covers the gold completely. At the surface the silver comes into contact with water and sulphur in the air, and corrodes. “This makes the gold surface of the “Zwischgold” turn black over time,” Watts explains. “The only thing you can do about this is to seal the surface with a varnish so the sulphur does not attack the silver and form silver sulphide.” The artisans using “Zwischgold” were aware of this problem from the start. They used resin, glue or other organic substances as a varnish. “But over hundreds of years this protective layer has decomposed, allowing corrosion to continue,” Wu explains.

The corrosion also encourages more and more silver to migrate to the surface creating a gap below the “Zwischgold”. “We were surprised how clearly this gap under the metal layer could be seen,” says Watts. Especially in the sample taken from Mary’s robe, the “Zwischgold” had clearly come away from the base layer. “This gap can cause mechanical instability, and we expect that in some cases it is only the protective coating over the “Zwischgold” that is holding the metal foil in place,” Wu warns. This is a massive problem for the restoration of historical artifacts, as the silver sulphide has become embedded in the varnish layer or even further down. “If we remove the unsightly products of corrosion, the varnish layer will also fall away and we will lose everything,” says Wu. She hopes it will be possible in future to develop a special material that can be used to fill the gap and keep the “Zwischgold” attached. “Using ptychographic tomography, we could check how well such a consolidation material would perform its task,” says the art historian.

Science paper:
Nanoscale
See the science paper for detailed material with images.

See the full article here.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Paul Sherrer Institute SwissFEL Coherent Light Source, Spallation Neutron Source (SINQ), Muon Source (SμS), X-ray free-electron laser (SwissFEL).

The Paul Scherrer Institute [Paul Scherrer Institut] (CH) is the largest research institute for natural and engineering sciences within Switzerland. We perform world-class research in three main subject areas: Matter and Material; Energy and the Environment; and Human Health. By conducting fundamental and applied research, we work on long-term solutions for major challenges facing society, industry and science.

The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the River Aare, and covers an area over 35 hectares in size. Like ETH Zurich [Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH) and EPFL [Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH)], PSI belongs to the Swiss Federal Institutes of Technology Domain of the Swiss Confederation . The PSI employs around 2100 people. It conducts basic and applied research in the fields of matter and materials, human health, and energy and the environment. About 37% of PSI’s research activities focus on material sciences, 24% on life sciences, 19% on general energy, 11% on nuclear energy and safety, and 9% on particle physics.
PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1900 experiments are conducted each year at the approximately 40 measuring stations in these facilities.

In recent years, the institute has been one of the largest recipients of money from the Swiss lottery fund.

Research and specialist areas

Paul Scherrer Institute develops, builds and operates several accelerator facilities, e. g. a 590 MeV high-current cyclotron, which in normal operation supplies a beam current of about 2.2 mA. PSI also operates four large-scale research facilities: a synchrotron light source (SLS), which is particularly brilliant and stable, a spallation neutron source (SINQ), a muon source (SμS) and an X-ray free-electron laser (SwissFEL).

This makes PSI currently (2020) the only institute in the world to provide the four most important probes for researching the structure and dynamics of condensed matter (neutrons, muons and synchrotron radiation) on a campus for the international user community. In addition, HIPA’s target facilities also produce pions that feed the muon source and the Ultracold Neutron source UCN produces very slow, ultracold neutrons. All these particle types are used for research in particle physics.

From The Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich](CH) and The Paul Scherrer Institute [Paul Scherrer Institut](CH): “Light amplification accelerates chemical reactions in aerosols”

From The Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich](CH)

and

The Paul Scherrer Institute [Paul Scherrer Institut](CH)

4.14.22
Fabio Bergamin

Aerosols in the atmosphere react to incident sunlight. This light is amplified in the interior of the aerosol droplets and particles, accelerating reactions. ETH researchers have now been able to demonstrate and quantify this effect and recommend factoring it into future climate models.

The Saharan dust that coloured Swiss skies in mid-​March was made up of mineral aerosols. But even outside of such extreme events, there are aerosols composed of mineral and organic compounds in the air. Photograph: Keystone-​SDA.

Liquid droplets and very fine particles can trap light – similar to how light can be caught between two mirrors. As a result, the intensity of the light inside them is amplified. This also happens in very fine water droplets and solid particles in our atmosphere, i.e. aerosols. Using modern X-​ray microscopy, chemists at ETH Zürich and the Paul Scherrer Institute have now investigated how light amplification affects photochemical processes that take place in the aerosols. They were able to demonstrate that light amplification causes these chemical processes to be two to three times faster on average than they would be without this effect.

Using the Swiss Light Source at the PSI, the researchers studied aerosols consisting of tiny particles of iron(III) citrate.

Paul Sherrer Institute SwissFEL Coherent Light Source

Exposure to light reduces this compound to iron(II) citrate. X-​ray microscopy makes it possible to distinguish areas within the aerosol particles composed of iron(III) citrate from those made up of iron(II) citrate down to a precision of 25 nanometres. In this way, the scientists were able to observe and map in high resolution the temporal sequence of this photochemical reaction in individual aerosol particles.

Decay upon exposure to light

“For us, iron(III) citrate was a representative compound that was easy to study with our method,” says Pablo Corral Arroyo, a postdoc in the group headed by ETH Professor Ruth Signorell and a lead author of the study. Iron(III) citrate stands in for a whole range of other chemical compounds that can occur in the aerosols of the atmosphere. Many organic and inorganic compounds are light-​sensitive, and when exposed to light, they can break down into smaller molecules, which can be gaseous and therefore escape. “The aerosol particles lose mass in this way, changing their properties,” Signorell explains. Among other things, they scatter sunlight differently, which affects weather and climate phenomena. In addition, their characteristics as condensation nuclei in cloud formation change.

As such, the results also have an effect on climate research. “Current computer models of global atmospheric chemistry don’t yet take this light amplification effect into account,” ETH Professor Signorell says. The researchers suggest incorporating the effect into these models in future.

Non-​uniform reaction times in the particles

Now precisely mapped and quantified, the light amplification in the particles comes about through resonance effects. The light intensity is greatest on the side of the particle opposite the one the light is shining on. “In this hotspot, photochemical reactions are up to ten times faster than they would be without the resonance effect,” says Corral Arroyo. Averaged over the entire particle, this gives an acceleration by the above-​mentioned factor of two to three. Photochemical reactions in the atmosphere usually last several hours or even days.

Using the data from their experiment, the researchers were able to create a computer model to estimate the effect on a range of other photochemical reactions of typical aerosols in the atmosphere. It turned out that the effect does not pertain just to iron(III) citrate particles, but all aerosols – particles or droplets – made of compounds that can react with light. And these reactions are also two to three times faster on average.

Science paper:
Science

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Paul Sherrer Institute SwissFEL Coherent Light Source, Spallation Neutron Source (SINQ), Muon Source (SμS), X-ray free-electron laser (SwissFEL).

The Paul Scherrer Institute [Paul Scherrer Institut] (CH) is the largest research institute for natural and engineering sciences within Switzerland. We perform world-class research in three main subject areas: Matter and Material; Energy and the Environment; and Human Health. By conducting fundamental and applied research, we work on long-term solutions for major challenges facing society, industry and science.

The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the River Aare, and covers an area over 35 hectares in size. Like ETH Zurich [Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH) and EPFL [Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH)], PSI belongs to the Swiss Federal Institutes of Technology Domain of the Swiss Confederation . The PSI employs around 2100 people. It conducts basic and applied research in the fields of matter and materials, human health, and energy and the environment. About 37% of PSI’s research activities focus on material sciences, 24% on life sciences, 19% on general energy, 11% on nuclear energy and safety, and 9% on particle physics.
PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1900 experiments are conducted each year at the approximately 40 measuring stations in these facilities.

In recent years, the institute has been one of the largest recipients of money from the Swiss lottery fund.

Research and specialist areas

Paul Scherrer Institute develops, builds and operates several accelerator facilities, e. g. a 590 MeV high-current cyclotron, which in normal operation supplies a beam current of about 2.2 mA. PSI also operates four large-scale research facilities: a synchrotron light source (SLS), which is particularly brilliant and stable, a spallation neutron source (SINQ), a muon source (SμS) and an X-ray free-electron laser (SwissFEL).

This makes PSI currently (2020) the only institute in the world to provide the four most important probes for researching the structure and dynamics of condensed matter (neutrons, muons and synchrotron radiation) on a campus for the international user community. In addition, HIPA’s target facilities also produce pions that feed the muon source and the Ultracold Neutron source UCN produces very slow, ultracold neutrons. All these particle types are used for research in particle physics.

The Swiss Federal Institute of Technology in Zürich [ETH Zürich] [Eidgenössische Technische Hochschule Zürich] (CH) is a public research university in the city of Zürich, Switzerland. Founded by the Swiss Federal Government in 1854 with the stated mission to educate engineers and scientists, the school focuses exclusively on science, technology, engineering and mathematics. Like its sister institution The Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne](CH) , it is part of The Swiss Federal Institutes of Technology Domain (ETH Domain)) , part of the The Swiss Federal Department of Economic Affairs, Education and Research [EAER][Eidgenössisches Departement für Wirtschaft, Bildung und Forschung] [Département fédéral de l’économie, de la formation et de la recherche] (CH).

The university is an attractive destination for international students thanks to low tuition fees of 809 CHF per semester, PhD and graduate salaries that are amongst the world’s highest, and a world-class reputation in academia and industry. There are currently 22,200 students from over 120 countries, of which 4,180 are pursuing doctoral degrees. In the 2021 edition of the QS World University Rankings ETH Zürich is ranked 6th in the world and 8th by the Times Higher Education World Rankings 2020. In the 2020 QS World University Rankings by subject it is ranked 4th in the world for engineering and technology (2nd in Europe) and 1st for earth & marine science.

As of November 2019, 21 Nobel laureates, 2 Fields Medalists, 2 Pritzker Prize winners, and 1 Turing Award winner have been affiliated with the Institute, including Albert Einstein. Other notable alumni include John von Neumann and Santiago Calatrava. It is a founding member of the IDEA League and the International Alliance of Research Universities (IARU) and a member of the CESAER network.

ETH Zürich was founded on 7 February 1854 by the Swiss Confederation and began giving its first lectures on 16 October 1855 as a polytechnic institute (eidgenössische polytechnische schule) at various sites throughout the city of Zurich. It was initially composed of six faculties: architecture, civil engineering, mechanical engineering, chemistry, forestry, and an integrated department for the fields of mathematics, natural sciences, literature, and social and political sciences.

It is locally still known as Polytechnikum, or simply as Poly, derived from the original name eidgenössische polytechnische schule, which translates to “federal polytechnic school”.

ETH Zürich is a federal institute (i.e., under direct administration by the Swiss government), whereas The University of Zürich [Universität Zürich ] (CH) is a cantonal institution. The decision for a new federal university was heavily disputed at the time; the liberals pressed for a “federal university”, while the conservative forces wanted all universities to remain under cantonal control, worried that the liberals would gain more political power than they already had. In the beginning, both universities were co-located in the buildings of the University of Zürich.

From 1905 to 1908, under the presidency of Jérôme Franel, the course program of ETH Zürich was restructured to that of a real university and ETH Zürich was granted the right to award doctorates. In 1909 the first doctorates were awarded. In 1911, it was given its current name, Eidgenössische Technische Hochschule. In 1924, another reorganization structured the university in 12 departments. However, it now has 16 departments.

ETH Zürich, EPFL (Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH), and four associated research institutes form The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) with the aim of collaborating on scientific projects.

Reputation and ranking

ETH Zürich is ranked among the top universities in the world. Typically, popular rankings place the institution as the best university in continental Europe and ETH Zürich is consistently ranked among the top 1-5 universities in Europe, and among the top 3-10 best universities of the world.

Historically, ETH Zürich has achieved its reputation particularly in the fields of chemistry, mathematics and physics. There are 32 Nobel laureates who are associated with ETH Zürich, the most recent of whom is Richard F. Heck, awarded the Nobel Prize in chemistry in 2010. Albert Einstein is perhaps its most famous alumnus.

In 2018, the QS World University Rankings placed ETH Zürich at 7th overall in the world. In 2015, ETH Zürich was ranked 5th in the world in Engineering, Science and Technology, just behind the Massachusetts Institute of Technology, Stanford University and University of Cambridge (UK). In 2015, ETH Zürich also ranked 6th in the world in Natural Sciences, and in 2016 ranked 1st in the world for Earth & Marine Sciences for the second consecutive year.

In 2016, Times Higher Education World University Rankings ranked ETH Zürich 9th overall in the world and 8th in the world in the field of Engineering & Technology, just behind the Massachusetts Institute of Technology, Stanford University, California Institute of Technology, Princeton University, University of Cambridge(UK), Imperial College London(UK) and University of Oxford(UK) .

In a comparison of Swiss universities by swissUP Ranking and in rankings published by CHE comparing the universities of German-speaking countries, ETH Zürich traditionally is ranked first in natural sciences, computer science and engineering sciences.

In the survey CHE Excellence Ranking on the quality of Western European graduate school programs in the fields of biology, chemistry, physics and mathematics, ETH Zürich was assessed as one of the three institutions to have excellent programs in all the considered fields, the other two being Imperial College London (UK) and the University of Cambridge (UK), respectively.

From The Paul Scherrer Institute [Paul Scherrer Institut](CH): “A look into the magnetic future”

From The Paul Scherrer Institute [Paul Scherrer Institut](CH)

4 April 2022
Written by Barbara Vonarburg

Contact

Prof. Dr. Laura Heyderman
Laboratory for Multiscale Materials Experiments
Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 26 13, e-mail: laura.heyderman@psi.ch [English, German, French]

Dr. Kevin Hofhuis
Department of Applied Physics, Yale University
217 Prospect St, New Haven, CT 06511, USA
E-Mail: kevin.hofhuis@yale.edu

Researchers at PSI have observed for the first time how tiny magnets in a special layout align themselves solely as a result of temperature changes. This view into processes that take place within so-called artificial spin ice could play an important role in the development of novel high-performance computers. The results were published today in the journal Nature Physics.

Scanning electron micrograph of the lithographically generated artificial kagome spin ice showing the nanoscale permalloy magnets asymmetrically connected by magnetic bridges. (Photograph: Kevin Hofhuis / PSI / ETH Zurich)

Laura Heyderman and Peter Derlet investigate magnetic phase transitions in matter. Photo: Markus Fischer/Paul Scherrer Institute.

When water freezes to form ice, the water molecules, with their hydrogen and oxygen atoms, arrange themselves in a complex structure. Water and ice are different phases, and the transformation from water to ice is called a phase transition. In the laboratory, crystals can be produced in which the elementary magnetic moments, the so-called spins, form structures comparable to ice. That is why researchers also refer to these structures as spin ice. “We have produced artificial spin ice, which essentially consists of nanomagnets that are so small that their orientation can only change as a result of temperature,” explains physicist Kevin Hofhuis, who has just completed his doctoral thesis at PSI and now works at Yale University in the USA.

In the material the researchers used, the nanomagnets are arranged in hexagonal structures – a pattern that is known from the Japanese art of basket weaving under the name kagome. “Magnetic phase transitions had been theoretically predicted for artificial kagome spin ice, but they have never been observed before,” says Laura Heyderman, the head of the Laboratory for Multiscale Materials Experiments at PSI and a professor at ETH Zurich. “The detection of phase transitions has only been made possible now thanks to the use of state-of-the-art lithography to produce the material in the PSI clean room as well as a special microscopy method at the Swiss Light Source SLS.” The journal Nature Physics is now publishing the results of these experiments.

Figure: (a) Scanning electron micrograph of the lithographically generated artificial kagome spin ice showing the nanoscale permalloy magnets asymmetrically connected by magnetic bridges. The smallest bridges are only 10 nanometres wide. (b) The resulting magnetic order is imaged with a photoemission electron microscope at the Swiss Light Source SLS. The magnetic configuration can be determined from the light-dark contrast and compared with computer simulations. Credit: Kevin Hofhuis.

The trick: tiny magnetic bridges

For their samples, the researchers used a nickel-iron compound called permalloy, which was coated as a thin film on a silicon substrate. They used a lithography process to repeatedly form a small, hexagonal pattern of nanomagnets, with each nanomagnet being approximately half a micrometre (millionths of a metre) long and one-sixth of a micrometre wide. But that’s not all. “The trick was that we connected the nanomagnets with tiny magnetic bridges,” says Hofhuis. “This led to small changes in the system that made it possible for us to tune the phase transition in such a way that we could observe it. However, these bridges had to be really small, because we didn’t want to change the system too much.”

The physicist is still amazed that this undertaking actually succeeded. With the creation of the nanobridges, he was pushing up against the limits of the technically possible spatial resolution of today’s lithography methods. Some of the bridges are only ten nanometres (billionths of a metre) across. The orders of magnitude in this experiment are indeed impressive, says Hofhuis: “While the smallest structures on our sample are in the nanometre range, the instrument for imaging them – SLS – has a circumference of almost 300 metres.” Heyderman adds: “The structures that we examine are 30 billion times smaller than the instruments with which we examine them.”

Microscopy and theory

At the SIM beamline of SLS, the team used a special method called photoemission electron microscopy that made it possible to observe the magnetic state of each individual nanomagnet in the array. They were actively supported by Armin Kleibert, the scientist in charge of SIM. “We were able to record a video that shows how the nanomagnets interact with each other as we change the temperature,” summarises Hofhuis. The original images simply contain black and white contrast that switched from time to time. From this, the researchers were able to deduce the configuration of the spins, that is, the alignment of the magnetic moments.

“If you watch a video like this, you don’t know what phase you’re in,” explains Hofhuis. This called for theoretical consideration, which was contributed by Peter Derlet, PSI physicist and adjunct professor at ETH Zurich. His simulations showed what should theoretically happen at the phase transitions. Only the comparison of the recorded images with these simulations proved that the processes observed under the microscope actually are phase transitions.

Manipulating phase transitions

The new study is another achievement in the investigation of artificial spin ice that Laura Heyderman’s group has been pursuing for more than a decade. “The great thing about these materials is that we can tailor them and see directly what is happening inside them,” the physicist says. “We can observe all sorts of fascinating behaviour, including the phase transitions and ordering that depend on the layout of the nanomagnets. This is not possible with spin systems in conventional crystals.” Although these investigations are still pure fundamental research at the moment, the researchers are already thinking about possible applications. “Now we know that we can see and manipulate different phases in these materials, new possibilities are opening up,” says Hofhuis.

Controlling different magnetic phases could be interesting for novel types of data processing. Researchers at PSI and elsewhere are investigating how the complexity of artificial spin ice could be used for novel high-speed computers with low power consumption. “The process is based on the information processing in the brain and takes advantage of how the artificial spin ice reacts to a stimulus such as a magnetic field or an electric current,” explains Heyderman.

See the full article here.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The Paul Scherrer Institute [Paul Scherrer Institut] (CH) is the largest research institute for natural and engineering sciences within Switzerland. We perform world-class research in three main subject areas: Matter and Material; Energy and the Environment; and Human Health. By conducting fundamental and applied research, we work on long-term solutions for major challenges facing society, industry and science.

The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the River Aare, and covers an area over 35 hectares in size. Like ETH Zurich [Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH) and EPFL [Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH)], PSI belongs to the Swiss Federal Institutes of Technology Domain of the Swiss Confederation . The PSI employs around 2100 people. It conducts basic and applied research in the fields of matter and materials, human health, and energy and the environment. About 37% of PSI’s research activities focus on material sciences, 24% on life sciences, 19% on general energy, 11% on nuclear energy and safety, and 9% on particle physics.
PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1900 experiments are conducted each year at the approximately 40 measuring stations in these facilities.

In recent years, the institute has been one of the largest recipients of money from the Swiss lottery fund.

Research and specialist areas

Paul Scherrer Institute develops, builds and operates several accelerator facilities, e. g. a 590 MeV high-current cyclotron, which in normal operation supplies a beam current of about 2.2 mA. PSI also operates four large-scale research facilities: a synchrotron light source (SLS), which is particularly brilliant and stable, a spallation neutron source (SINQ), a muon source (SμS) and an X-ray free-electron laser (SwissFEL).

Paul Sherrer Institute SwissFEL Coherent Light Source, Spallation Neutron Source (SINQ), Muon Source (SμS), X-ray free-electron laser (SwissFEL)

This makes PSI currently (2020) the only institute in the world to provide the four most important probes for researching the structure and dynamics of condensed matter (neutrons, muons and synchrotron radiation) on a campus for the international user community. In addition, HIPA’s target facilities also produce pions that feed the muon source and the Ultracold Neutron source UCN produces very slow, ultracold neutrons. All these particle types are used for research in particle physics.

From The Paul Scherrer Institute [Paul Scherrer Institut](CH): “Towards compact quantum computers thanks to topology”

From The Paul Scherrer Institute [Paul Scherrer Institut](CH)

20 January 2022
Laura Hennemann

Researchers at The Paul Scherrer Institute [Paul Scherrer Institut](CH) have compared the electron distribution below the oxide layer of two semiconductors. The investigation is part of an effort to develop particularly stable quantum bits –and thus, in turn, particularly efficient quantum computers. They have now published their latest research, which is supported in part by Microsoft, in the scientific journal Advanced Quantum Technologies.

By now the future of computing is inconceivable without quantum computers. For the most part, these are still in the research phase. They hold the promise of speeding up certain calculations and simulations by orders of magnitude compared to classical computers.

Quantum bits-or qubits for short-form the basis of quantum computers. So-called topological quantum bits are a novel type that might prove to be superior. To find out how these could be created, an international team of researchers has carried out measurements at the Swiss Light Source SLS at The Paul Scherrer Institute [Paul Scherrer Institut](CH).

Niels Schröter (left) and Vladimir Strocov at one of the experiment stations of the Swiss Light Source SLS at PSI. Here the researchers used soft X-ray angle-resolved photoelectron spectroscopy to measure the electron distribution below the oxide layer of indium arsenide as well as indium antimonide.
Photo: Mahir Dzambegovic/Paul Scherrer Institute.

More stable quantum bits

Gabriel Aeppli, head of the Photon Science Division at PSI, specialises in the study of quantum materials.
Photo: Thomas Baumann.

“Computer bits that follow the laws of quantum mechanics can be achieved in different ways,” explains Niels Schröter, one of the study’s authors. He was a researcher at PSI until April 2021, when he moved to The MPG Institute of Microstructure Physics [MPG für Mikrostrukturphysik] (DE). “Most types of qubits unfortunately lose their information quickly; you could say they are forgetful qubits.” There is a technical solution to this: Each qubit is backed up with a system of additional qubits that correct any errors that occur. But this means that the total number of qubits needed for an operational quantum computer quickly rises into the millions.

“Microsoft’s approach, which we are now collaborating on, is quite different,” Schröter continues. “We want to help create a new kind of qubit that is immune to leakage of information. This would allow us to use just a few qubits to achieve a slim, functioning quantum computer.”

The researchers hope to obtain such immunity with so-called topological quantum bits. These would be something completely new that no research group has yet been able to create.

Topological materials became more widely known through the Nobel Prize in Physics in 2016. Topology is originally a field of mathematics that explores, among other things, how geometric objects behave when they are deformed. However, the mathematical language developed for this can also be applied to other physical properties of materials. Quantum bits in topological materials would then be topological qubits.

Quasiparticles in semiconductor nanowires

It is known that thin-film systems of certain semiconductors and superconductors could lead to exotic electron states that would act as such topological qubits. Specifically, ultra-thin, short wires made of a semiconductor material could be considered for this purpose. These have a diameter of only 100 nanometres and are 1,000 nanometres (i.e., 0.0001 centimetres) long. On their outer surface, in the longitudinal direction, the top half of the wires is coated with a thin layer of a superconductor. The rest of the wire is not coated so that a natural oxide layer forms there. Computer simulations for optimising these components predict that the crucial, quantum mechanical electron states are only located at the interface between the semiconductor and the superconductor and not between the semiconductor and its oxide layer.

“The collective, asymmetric distribution of electrons generated in these nanowires can be physically described as so-called quasiparticles,” says Gabriel Aeppli, head of the Photon Science Division at PSI, who was also involved in the current study. “Now, if suitable semiconductor and superconductor materials are chosen, these electrons should give rise to special quasiparticles called Majorana fermions at the ends of the nanowires.”

Majorana fermions are topological states. They could therefore act as information carriers, ergo as quantum bits in a quantum computer. “Over the course of the last decade, recipes to create Majorana fermions have already been studied and refined by research groups around the world,” Aeppli continues. “But to continue with this analogy: we still didn’t know which cooking pot would give us the best results for this recipe.”

Indium antimonide has the advantage

A central concern of the current research project was therefore the comparison of two “cooking pots”. The researchers investigated two different semiconductors and their natural oxide layer: on the one hand indium arsenide and on the other indium antimonide.

At SLS the PSI researchers used an investigation method called soft X-ray angle-resolved photoelectron spectroscopy – SX-ARPES for short. A novel computer model developed by Noa Marom’s group at Carnegie Mellon University, USA, together with Vladimir Strocov from PSI, was used to interpret the complex experimental data. “The computer models used up to now led to an unmanageably large number of spurious results. With our new method, we can now look at all the results, automatically filter out the physically relevant ones, and properly interpret the experimental outcome,” explains Strocov.

Through their combination of SX-ARPES experiments and computer models, the researchers have now been able to show that indium antimonide has a particularly low electron density below its oxide layer. This would be advantageous for the formation of topological Majorana fermions in the planned nanowires.

“From the point of view of electron distribution under the oxide layer, indium antimonide is therefore better suited than indium arsenide to serve as a carrier material for topological quantum bits,” concludes Niels Schröter. However, he points out that in the search for the best materials for a topological quantum computer, other advantages and disadvantages must certainly be weighed against each other. “Our advanced spectroscopic methods will certainly be instrumental in the quest for the quantum computing materials,” says Strocov. “PSI is currently taking big steps to expand quantum research and engineering in Switzerland, and SLS is an essential part of that.”

See the full article here.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The Paul Scherrer Institute [Paul Scherrer Institut] (CH) is the largest research institute for natural and engineering sciences within Switzerland. We perform world-class research in three main subject areas: Matter and Material; Energy and the Environment; and Human Health. By conducting fundamental and applied research, we work on long-term solutions for major challenges facing society, industry and science.

The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the River Aare, and covers an area over 35 hectares in size. Like ETH Zurich [Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH) and EPFL (Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH)], PSI belongs to the The Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH). The PSI employs around 2100 people. It conducts basic and applied research in the fields of matter and materials, human health, and energy and the environment. About 37% of PSI’s research activities focus on material sciences, 24% on life sciences, 19% on general energy, 11% on nuclear energy and safety, and 9% on particle physics.

PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1900 experiments are conducted each year at the approximately 40 measuring stations in these facilities.

In recent years, the institute has been one of the largest recipients of money from the Swiss lottery fund.

Research and specialist areas

Paul Scherrer Institute develops, builds and operates several accelerator facilities, e. g. a 590 MeV high-current cyclotron, which in normal operation supplies a beam current of about 2.2 mA. PSI also operates four large-scale research facilities: a synchrotron light source (SLS), which is particularly brilliant and stable, a spallation neutron source (SINQ), a muon source (SμS) and an X-ray free-electron laser (SwissFEL).

Paul Sherrer Institute SwissFEL Coherent Light Source, Spallation Neutron Source (SINQ), Muon Source (SμS), X-ray free-electron laser (SwissFEL)

This makes PSI currently (2020) the only institute in the world to provide the four most important probes for researching the structure and dynamics of condensed matter (neutrons, muons and synchrotron radiation) on a campus for the international user community. In addition, HIPA’s target facilities also produce pions that feed the muon source and the Ultracold Neutron source UCN produces very slow, ultracold neutrons. All these particle types are used for research in particle physics.

From The Paul Scherrer Institute [Paul Scherrer Institut](CH) : “The world’s most powerful neutron microscope”

From The Paul Scherrer Institute [Paul Scherrer Institut](CH)

14 December 2021
Text: Jan Berndorff

Contact
Prof. Marc Janoschek
Acting head of the Research with Neutrons and Muons Division
Head of the Laboratory for Neutron and Muon Instrumentation
Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 49 87
marc.janoschek@psi.ch

Researchers from the Paul Scherrer Institute PSI in Villigen have delivered a key component for the ESTIA reflectometer at the European Spallation Source ESS based in Lund, Sweden.

ESS European Spallation Source in Lund, Sweden.

When it comes into service in 2026 ESS will be the world’s most powerful neutron source. Switzerland is making a vital contribution to the project. Scientists from across the globe will use ESS instruments to study processes and structures on the atomic scale, advancing materials research to a new level.

Marc Janoschek is leading the PSI project to build the ESTIA reflectometer at the European Spallation Source ESS. Here he stands at a component of the facility. Photo: Mahir Dzambegovic/Paul Scherrer Institute.

The European Spallation Source ESS currently under construction is in a class of its own, delivering a neutron beam of unrivalled intensity that opens new research opportunities. One of 15 instruments in total being installed at ESS, the ESTIA reflectometer is gradually taking shape. Reflectometers measure reflections or the reflection angles of neutrons at boundary layers and surfaces for non-destructive testing of their properties. PSI is solely responsible for constructing and operating ESTIA. It has just delivered the first part of an important optics component: the Selene neutron guide, which provides a particularly high-intensity beam for investigating material samples.

A project this big needs many people involved, including (from left to right): Marc Janoschek, Alessandra Luchini, Artur Glavic, André Schwarb, Zeljka Budrovic, Peter Heimgartner, Achim Ammon, Thomas Mühlebach, Roman Kaminski, Sven Schütz, Harald Siebold.
Photo: Mahir Dzambegovic/Paul Scherrer Institute.

Neutron sources constitute large research facilities. They provide an intense neutron beam which can be used with different instruments for non-destructive testing of processes and structures on the nanoscale, increasing our understanding of materials. They can be used, for example, to investigate metal components or archaeological artefacts, analyse biomolecular processes or the electronic structure and dynamics of novel superconductors, or solve the remaining puzzles of elementary particle physics. More powerful beams allow even smaller samples to be illuminated, providing even greater detail about the structures and processes within a sample.

Artur Glavic, Alessandra Luchini and Sven Schütz (from left to right) are pleased to have succeeded in the logistical feat of setting up the ESTIA reflectometer at the ESS.
Photo: Mahir Dzambegovic/Paul Scherrer Institute.

The ESS facility produces neutrons through a process of spallation: protons are fired at a tungsten plate, shattering its atomic nuclei and releasing neutrons in the process. This avoids having to use a nuclear reactor – clearly a big advantage. “In addition, we can continue to develop spallation further, which was not possible with the conventional method for producing neutrons dating from the 1950s,” says Marc Janoschek, Head of PSI’s Laboratory for Neutron and Muon Instrumentation (LIN) and ESTIA project manager. “It provides a higher intensity neutron beam, and furthermore spallation sources can be operated in pulse mode. In combination, these two characteristics deliver a higher neutron flow with superior temporal and spatial resolution, allowing faster and more accurate measurements.”

A large-scale multinational project

A total of 13 nations are involved in the ESS project, each contributing their specialist expertise. Switzerland’s skill set is particularly wide-ranging, as PSI is already experienced in operating this type of facility, having been home to the world’s only spallation neutron source, SINQ, on its research campus for some time. All other spallation sources in service at present work with neutron pulses. Apart from ESTIA, PSI is currently collaborating with other international research institutes on four other instruments being constructed at the ESS: the BIFROST extreme environment spectrometer, the HEIMDAL hybrid diffractometer, the ODIN multi-purpose imaging instrument and the MAGIC magnetism single-crystal diffractometer. PSI is building instruments with a total value of €35 million.

PSI researchers and engineers are ideally suited to their role as sole developers of ESTIA since they already operate a very similar instrument in Switzerland: the AMOR reflectometer. Reflectometers shoot the neutron beam specifically at the interface and surface layers of two or more materials. The neutrons penetrate the material and are scattered by their structures. This scattering is captured by detectors and the reflection angles calculated and analysed. They provide information about the composition of the scattering atoms and their arrangement in relation to one another. Because the neutrons interact with the atomic nuclei rather than with the electrons in the atomic shell (as is the case with X-rays), it is even possible to locate and identify isotopes of one material penetrating the other with nanometre precision. Irregularities in a material or a boundary layer can thus be detected with a high degree of accuracy.

Boundary layers are central to understanding many materials and their behaviour in use. For example, the diffusion of lithium ions at boundary layers is crucial for battery performance. In semiconductors, the interfaces of the materials are also important, and in sensors and magnetic storage devices, the magnetic properties of the interfaces play a key role. Even in basic research, exciting and previously unknown phenomena come to light, explains Alessandra Luchini, lead scientist for ESTIA: “For example, two previously non-magnetic materials suddenly become magnetic at their interface, or the superconductive temperature of a superconductor rises from 10 to 100 Kelvin on a specific substrate.” This shows that research into magnetic and structural boundary layers is also important for future applications. ESTIA provides the platform for studying these effects on a realistic scale – namely with sample sizes similar to the situations the materials are actually used in.

Swiss precision

The AMOR reflectometer at PSI in Villigen offers extremely high precision thanks to the Selene guide developed in house at PSI. “The intensity of the beam is around 30 times greater than other reflectors,” says ESTIA’s head engineer, Sven Schütz. “And when we install this technology at ESTIA in Lund we will be able to boost this power even further.”

The Selene focusing guide occupies around 24 metres of the ESTIA instrument, whose total length is 39 metres. Its function is to focus the neutron beam on the sample with even greater intensity. In the past this has been a drawback compared with X-ray microscopes. Modern synchrotron sources enable all samples to be studied on the micrometre scale because their electromagnetic radiation, produced by electrons in strong magnetic fields, is automatically brilliant. By contrast, neutron beams require intense focusing beforehand to study small samples. “With AMOR, we use two 18m-long elliptical neutron mirrors installed in series. These consist of highly polished glass substrates onto which metal layers have been vapour-deposited, which reflect the neutrons,” PSI-ESS project manager Artur Glavic explains. This allows the beam to be controlled like a lens to direct the focus onto samples as small as one square millimetre. Without the Selene guide, only centimetre-sized objects could be measured. This is not enough to produce useful information when studying minute items such as computer chips, which are getting smaller and smaller.

Two trucks transporting the apparatus from Switzerland to the ESS construction site have now arrived in Lund. They constitute the first half of the support frame for the Selene focusing guide. The second part is scheduled for delivery between March and May 2022. Sven Schütz and Alessandra Luchini are supervising installation on site. The guide is fitted with measurement and calibration robots so that it can be remotely controlled within the safety screens, as the installation is under vacuum, and the neutron beam is too powerful for direct intervention. The Selene module is due to be fully integrated by the end of 2022, and ESTIA will be one of the first instruments to start operation at ESS in 2024.

Precision work despite the pandemic

One reason for setting up the instrument well in advance is to ensure greater precision: ESS is built on a complex foundation of concrete pillars which takes time to settle. If the Selene guide is installed soon enough, it will settle at the same rate, eventually providing an even higher degree of accuracy. “Such punctual delivery of the first components was a huge logistical feat and is mainly down to the efforts of Artur Glavic, Alessandra Luchini and Sven Schütz,” says Marc Janoschek.

But the effort is definitely worth it. Not just ESTIA in particular, but also ESS as a whole will help advance Swiss research. Switzerland’s State Secretariat for Education, Research and Innovation SERI is contributing 64.5 million euros, or 3.5 percent of the total ESS construction costs of more than 1.8 billion euros. In addition, the running costs amount to some 800 million euros up to 2026, and around 140 million per year when the whole facility eventually goes live. Switzerland will cover nearly four percent of the running costs as well. “Our intention is not simply to contribute our know-how to the operation of such a complex facility,” Marc Janoschek comments. “Switzerland also wants to allow its brightest talents access to this large research facility, the only one of its type in the world, so we can continue to be actively involved in leading-edge international research.”

[Will the U.S.A. answer?
The U.S.A. has

ORNL Spallation Neutron Source annotated.

The first three of the Spallation Neutron Source instruments began commissioning and were available to the scientific community in August 2007.]

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The Paul Scherrer Institute [Paul Scherrer Institut](CH) is the largest research institute for natural and engineering sciences within Switzerland. We perform world-class research in three main subject areas: Matter and Material; Energy and the Environment; and Human Health. By conducting fundamental and applied research, we work on long-term solutions for major challenges facing society, industry and science.

The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute for natural and engineering sciences in Switzerland. It is located in the Canton of Aargau in the municipalities Villigen and Würenlingen on either side of the River Aare, and covers an area over 35 hectares in size. Like ETH Zurich and EPFL, PSI belongs to the Swiss Federal Institutes of Technology Domain of the Swiss Confederation. The PSI employs around 2100 people. It conducts basic and applied research in the fields of matter and materials, human health, and energy and the environment. About 37% of PSI’s research activities focus on material sciences, 24% on life sciences, 19% on general energy, 11% on nuclear energy and safety, and 9% on particle physics.

PSI develops, builds and operates large and complex research facilities and makes them available to the national and international scientific communities. In 2017, for example, more than 2500 researchers from 60 different countries came to PSI to take advantage of the concentration of large-scale research facilities in the same location, which is unique worldwide. About 1900 experiments are conducted each year at the approximately 40 measuring stations in these facilities.

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