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  • richardmitnick 10:19 am on April 5, 2018 Permalink | Reply
    Tags: A New State of Quantum Matter Has Been Found in a Material Scientists Thought Was All Chaos, , Photoemission electron microscopy, , , Quasiparticles, , Shakti geometry, Spin ice   

    From Science Alert: “A New State of Quantum Matter Has Been Found in a Material Scientists Thought Was All Chaos” 

    ScienceAlert

    Science Alert

    5 APR 2018
    MIKE MCRAE

    1
    (enot-poloskun/istock)

    What else is lurking in there?

    Experiments carried out on a complex arrangement of magnetic particles have identified a completely new state of matter, and it can only be explained if scientists turn to quantum physics.

    The messy structures behind the research show strange properties that could allow us to study the chaos of exotic particles – if researchers can find order in there, it could help us understand these particles in greater detail, opening up a whole new landscape for quantum technology.

    Physicists from the US carried out their research on the geometrical arrangements of particles in a weird material known as spin ice.

    Like common old water ice, the particles making up spin ice sort themselves into geometric patterns as the temperature drops.

    There are a number of compounds that can be used to build this kind of material, but they all share the same kind of quantum property – their individual magnetic ‘spin’ sets up a bias in how the particles point to one another, creating complex structures.

    So, unlike the predictable crystalline patterns in water ice, the nanoscale magnetic particles making up spin ice can look disordered and chaotic under certain conditions, flipping back and forth wildly.

    The researchers focussed on one particular structure called a Shakti geometry, and measured how its magnetic arrangements fluctuated with changes in temperature.

    States of matter are usually broken down into categories such as solid, liquid, and gas. We’re taught on a fundamental level that a material’s volume and fluidity can change with shifts in its temperature and pressure.

    But there’s another way to think of a state of matter – by considering the points at which there’s a dramatic change in the way particles arrange themselves as they gain or lose energy.

    For example, the freezing of water is one such dramatic change – a sudden restructuring that occurs as pure water is chilled below 0 degrees Celsius (32 degrees Fahrenheit), where its molecules lose the energy they need to remain free and adopt another stable configuration.

    When researchers slowly lowered the temperature on spin ice arranged in a Shakti geometry, they got it to produce a similar behaviour – one that has never been seen before in other forms of spin ice.

    Using a process called photoemission electron microscopy, the team was then able to image the changes in pattern based on how their electrons emitted light.

    They were noticing points at which a specific arrangement persisted even as the temperature continued to drop.

    “The system gets stuck in a way that it cannot rearrange itself, even though a large-scale rearrangement would allow it to fall to a lower energy state,” says senior researcher Peter Schiffer, currently at Yale University.

    Such a ‘sticking point’ is a hallmark of a state of matter, and one that wasn’t expected in the flip-flopping madness of spin ice.

    Most states of matter can be described fairly efficiently using classical models of thermodynamics, with jiggling particles overcoming binding forces as they swap heat energy.

    In this case there was no clear model describing what was balancing the changes in energy with the material’s stable arrangement.

    So the team applied a quantum touch, looking at how entanglement between particles aligned to give rise to a particular topology, or pattern within a changing space.

    “Our research shows for the first time that classical systems such as artificial spin ice can be designed to demonstrate topological ordered phases, which previously have been found only in quantum conditions,” says physicist Cristiano Nisoli from Los Alamos National Laboratory.

    Ten years ago, quasiparticles that behaved like magnetic monopoles [Nature] were observed in another type of spin ice, also pointing at a weird kind of phase transition.

    Quasiparticles are becoming big things in our search for new kinds of matter that behaves in odd but useful ways, as they have pontential to be used in quantum computing. So having better models for understanding this quantum landscape will no doubt come in handy.

    This research was published in Nature.

    See the full article here .

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  • richardmitnick 2:05 pm on December 10, 2017 Permalink | Reply
    Tags: , , , New manifestation of magnetic monopoles discovered, , Quasiparticles   

    From IST Austria: “New manifestation of magnetic monopoles discovered” 

    Institute of Science and Technology Austria

    December 7, 2017

    Significant effort has gone into engineering the long-sought magnetic monopoles. Now scientists have found them in an unexpected place, and revealed that they have been around for a long time.

    1

    The startling similarity between the physical laws describing electric phenomena and those describing magnetic phenomena has been known since the 19th century. However, one piece that would make the two perfectly symmetric was missing: magnetic monopoles. While magnetic monopoles in the form of elementary particles remain elusive, there have been some recent successes in engineering objects that behave effectively like magnetic monopoles. Now, scientists at the Institute of Science and Technology Austria (IST Austria) have shown that there is a much simpler way to observe such magnetic monopoles: they have demonstrated that superfluid helium droplets act as magnetic monopoles from the perspective of molecules that are immersed inside them. Such droplets have been studied for decades, but until now, this fascinating characteristic had gone entirely unnoticed.

    When working with electric charge, it is easy to separate the positive and negative poles: the negatively charged electron represents a negative pole, the positively charged proton is the opposite (positive) pole, and each one is an individual particle that can be separated from the other. With magnets, it seemed that they always have two poles that are impossible to separate: cut a dipole magnet in half and you will end up with two dipole magnets, cut them again and you will just get even smaller dipole magnets, but you will not be able to separate the north from the south pole. Challenged by this puzzle, scientists put a great deal of effort into constructing systems that effectively act as magnetic monopoles—with success: certain crystal structures were made to behave like magnetic monopoles. But now, an interdisciplinary team comprising theoretical physicists and a mathematician have discovered that this phenomenon also occurs in molecular systems that do not need to be engineered for this purpose but which have been known of for a long time.

    Nanometer-sized drops of superfluid helium with molecules immersed in them have been studied for several decades already, and it is one of the systems that Professor Mikhail Lemeshko and postdoc Enderalp Yakaboylu are particularly interested in. Previously, Professor Lemeshko proposed a new quasiparticle that drastically simplifies the mathematical description of such rotating molecules, and earlier this year he showed that this quasiparticle, the angulon, can explain observations that had been collected over 20 years. Enderalp Yakaboylu moreover used the angulon to predict previously unknown properties of these systems. The property in superfluid helium droplets that they now discovered, however, came unexpectedly—and only after they had exchanged ideas with mathematician Andreas Deuchert, who says: “It was a surprise to all of us to see this characteristic emerge in the equations.” At a strongly interdisciplinary institute like IST Austria, such collaborations are not unusual, and interaction between research groups of different fields is fostered.

    “In the other experiments they engineered a system to become a monopole. Here, it is the other way round,” Enderalp Yakaboylu adds. “The system was well-known. People have been studying rotating molecules for a long time, and only after did we realize that the magnetic monopoles had been there the whole time. This is a completely different viewpoint.”

    According to the researchers, the discovery opens up new possibilities for studying magnetic monopoles. In particular, the appearance of magnetic monopole in superfluid helium droplets is very different from the other, previously studied, systems. “The difference is that we are dealing with a chemical solvent. Our magnetic monopoles form in a fluid rather than in a solid crystal, and you can use this system to study magnetic monopoles more easily,” Professor Mikhail Lemeshko explains.

    Science paper:
    Emergence of Non-Abelian Magnetic Monopoles in a Quantum Impurity Problem
    Physical Review Letters

    See the full article here.

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    The Institute of Science and Technology Austria (IST Austria) is a young international institute dedicated to basic research and graduate education in the natural and mathematical sciences, located in Klosterneuburg on the outskirts of Vienna. Established jointly by the federal government of Austria and the provincial government of Lower Austria, the Institute was inaugurated in 2009 and will grow to about 90 research groups by 2026.

    The governance and management structures of IST Austria guarantee its independence and freedom from political and commercial influences. The Institute is headed by the President, who is appointed by the Board of Trustees and advised by the Scientific Board. The first President of IST Austria is Thomas A. Henzinger, a leading computer scientist and former professor of the University of California at Berkeley and the EPFL Lausanne in Switzerland.

     
  • richardmitnick 8:43 am on October 12, 2016 Permalink | Reply
    Tags: , , Quasiparticles,   

    From Science Alert: “Physicists just witnessed quasiparticles forming for the first time ever” 

    ScienceAlert

    Science Alert

    11 OCT 2016
    FIONA MACDONALD

    1
    IQOQI/Harald Ritsch

    It’s a glorious moment for science.

    For the first time, scientists have observed the formation of quasiparticles – a strange phenomenon observed in certain solids – in real time, something that physicists have been struggling to do for decades.

    It’s not just a big deal for the physics world – it’s an achievement that could change the way we build ultra-fast electronics, and could lead to the development of quantum processors.

    But what is a quasiparticle? Rather than being a physical particle, it’s a concept used to describe some of the weird phenomena that happen in pretty fancy setups – specifically, many-body quantum systems, or solid-state materials.

    An example is an electron moving through a solid. As it the electron travels, it generates polarisation in its environment because of its electrical charge. This ‘polarisation’ cloud follows the electron through the material, and together they can be described as a quasiparticle.

    “You could picture it as a skier on a powder day,” explained one of the researchers, Rudolf Grimm, from the University of Innsbruck in Austria. “The skier is surrounded by a cloud of snow crystals. Together they form a system that has different properties than the skier without the cloud.”

    Quasiparticles and their formation have been extensively described in theoretical models, but actually measuring and observing them in real time has been a real challenge. That’s because not only is the quasiparticle phenomenon happening on a tiny scale – it’s also incredible short-lived.

    “These processes last only attoseconds, which makes a time-resolved observation of their formation extremely difficult,” said Grimm.

    To put that into perspective, 1 attosecond is one-quintillionth of a second. Which means 1 attosecond is to 1 second what 1 second is to about 31.71 billion years – so, yeah, that’s pretty fast.

    But the team managed to come up with a way to slow the process down a bit.

    Inside a vacuum chamber, they used laser trapping techniques to create an ultracold quantum gas made up of lithium atoms and a small sample of potassium atoms in the centre.

    They then used a magnetic field to tune interactions of the particles, creating a type of quasiparticle known as a Fermi polaron – which is basically potassium atoms embedded in a lithium cloud.

    The formation of those quasiparticles would have taken on the order of 100 attoseconds in a normal system, but thanks to the ultracold quantum gas, the team was able to slow it down, and witness it happening for the first time ever.

    “We simulated the same physical processes at much lower densities,” said Grimm. “Here, the formation time for polarons is a few microseconds.”

    The goal now is to figure out how to not only observe these quasiparticles, but actually measure them, so that we can find a way to use them to develop quantum processing systems that will bring us the super-fast electronics of the future.

    “We developed a new method for observing the ‘birth’ of a polaron virtually in real time,” said Grimm. “This may turn out to be a very interesting approach to better understand the quantum physical properties of ultrafast electronic devices.”

    The research has been published in Science.

    See the full article here .

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