From M.I.T. : “How to treat heat like light”

January 11, 2013
David L. Chandler

“An MIT researcher has developed a technique that provides a new way of manipulating heat, allowing it to be controlled much as light waves can be manipulated by lenses and mirrors.
The approach relies on engineered materials consisting of nanostructured semiconductor alloy crystals. Heat is a vibration of matter — technically, a vibration of the atomic lattice of a material — just as sound is. Such vibrations can also be thought of as a stream of phonons — a kind of “virtual particle” that is analogous to the photons that carry light. The new approach is similar to recently developed photonic crystals that can control the passage of light, and phononic crystals that can do the same for sound.

Thermal lattices, shown here, are one possible application of the newly developed thermocrystals. In these structures, where precisely spaced air gaps (dark circles) control the flow of heat, thermal energy can be “pinned” in place by defects introduced into the structure (colored areas).
Image courtesy of the researchers

The spacing of tiny gaps in these materials is tuned to match the wavelength of the heat phonons, explains Martin Maldovan, a research scientist in MIT’s Department of Materials Science and Engineering and author of a paper on the new findings published Jan. 11 in the journal Physical Review Letters.”

See the full article here.

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From MIT News: “A one-way street for spinning atoms”

Work correlating ultracold atoms’ spin with their direction of motion may help physicists model new circuit devices and unusual phases of matter.

August 30, 2012
News Office

“Elementary particles have a property called spin that can be thought of as rotation around their axes. In work reported this week in the journal Physical Review Letters, MIT physicists have imposed a stringent set of traffic rules on atomic particles in a gas: Those spinning clockwise can move in only one direction, while those spinning counterclockwise can move only in the other direction.

Elementary particles have a fundamental property called ‘spin’ that determines how they align in a magnetic field. MIT researchers have created a new physical system in which atoms with clockwise spin move in only one direction, while atoms with counterclockwise spin move in the opposite direction.
Graphic: Christine Daniloff

Physical materials with this distinctive property could be used in “spintronic” circuit devices that rely on spin rather than electrical current for transferring information. The correlation between spin and direction of motion is crucial to creating a so-called topological superfluid, a key ingredient of some quantum-computing proposals.

The MIT team, led by Martin Zwierlein, an associate professor of physics and a principal investigator in the Research Laboratory of Electronics (RLE), produced this spin-velocity correlation in an ultracold, dilute gas of atoms.

The MIT research was funded in part by the National Science Foundation, the Air Force Office of Scientific Research, the Office of Naval Research, the Army Research Office with funding from the DARPA Optical Lattice Emulator program, and the David and Lucile Packard Foundation.

See the full and important article here.

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From MIT News: “Alan Guth wins $3 million Fundamental Physics Prize”

“Alan Guth ’69, SM ’69, PhD ’72, the Victor F. Weisskopf Professor of Physics at MIT, is among nine physicists worldwide selected as inaugural winners of the Fundamental Physics Prize, the Milner Foundation announced today.

Congratulations to this graduate of Highland Park High School, Highland Park, NJ, USA, which also educated Eric, Jodi and Josh. What can I say, I could not let this go by.

This year’s recipients — each of whom will receive $3 million in recognition of past research achievements in physics — will form a selection committee for future winners of the Fundamental Physics Prize. After this year, it is expected that the prize will be awarded to one physicist annually for what the Milner Foundation described in a statement as ‘transformative advances in the field.’”

From MIT News: “Single-photon transmitter could enable new quantum devices”

July 25, 2012
David L. Chandler

Long-sought goal for quantum devices — the ability to transmit single photons while blocking multiple photons — is finally achieved.

“In theory, quantum computers should be able to perform certain kinds of complex calculations much faster than conventional computers, and quantum-based communication could be invulnerable to eavesdropping. But producing quantum components for real-world devices has proved to be fraught with daunting challenges.

An artist’s conception shows how any number of incoming photons (top) can be absorbed by a cloud of ultra-cold atoms (center), tuned so that only one single photon can pass through at a time. Being able to produce a controlled beam of single photons has been a goal of research toward creating quantum devices. Graphic: Christine Daniloff

Now, a team of researchers at MIT and Harvard University has achieved a crucial long-term goal of such efforts: the ability to convert a laser beam into a stream of single photons, or particles of light, in a controlled way. The successful demonstration of this achievement is detailed in a paper published this week in the journal Nature by MIT doctoral student Thibault Peyronel and colleagues.

See the full article here.

From M.I.T.: “NSE fusion program moves beyond plasma, towards practical power-plant issues”

“Nuclear fusion is a seemingly ideal energy source: carbon-free, fuel derived largely from seawater, no risk of runaway reactors and minimal waste issues. And the MIT Department of Nuclear Science and Engineering’s (NSE) long-standing fusion program is extending its leadership role in advancing the technology toward practical use.

NSE’s Plasma Science and Fusion Center (PFSC), home of one of just three U.S. tokamak fusion reactors, has been a focal point of fusion research since its founding in 1976, developing substantial basic knowledge about creating and maintaining fusion reactions. And today, explains Professor Dennis Whyte, NSE’s fusion team is beginning a strategic pivot into the next stage of development, with a focus on interdisciplinary knowledge needed for the creation of functioning
powerplants.

A tokamak

‘We’re basically making energy by creating a star,’ explains Whyte. ‘For power generation, the star has to turn on, and stay on for a year at a time, and we need a way to extract the energy it creates.’”

See the full article here.

From MIT News: “A new way to build nanostructures”

Combining top-down and bottom-up approaches, new low-cost method could be a boon to research with a variety of applications.

David L. Chandler, MIT News Office
July 6, 2011

“The making of three-dimensional nanostructured materials — ones that have distinctive shapes and structures at scales of a few billionths of a meter — has become a fertile area of research, producing materials that are useful for electronics, photonics, phononics and biomedical devices. But the methods of making such materials have been limited in the 3-D complexity they can produce. Now, an MIT team has found a way to produce more complicated structures by using a blend of current “top-down” and “bottom-up” approaches.

The work is described in a paper published in June in the journal Nano Letters, co-authored by postdoc Chih-Hao Chang; George Barbastathis, the Singapore Research Professor of Optics and Professor of Mechanical Engineering; and six MIT graduate students.

The new 3D nanofabrication method makes it possible to manufacture complex multi-layered solids all in one step. In this example, seen in these Scanning Electron Microscope images, a view from above (at top) shows alternating layers containing round holes and long bars. As seen from the side (lower image), the alternating shapes repeat through several layers. Image: Chih-Hao Chang

See the full article here.

From MIT News: “Toward faster transistors”

MIT physicists discover a new physical phenomenon that could eventually lead to the first increases in computers’ clock speed since 2002.

Larry Hardesty, MIT News Office

“In the 1980s and ’90s, competition in the computer industry was all about “clock speed” — how many megahertz, and ultimately gigahertz, a chip could boast. But clock speeds stalled out almost 10 years ago: Chips that run faster also run hotter, and with existing technology, there seems to be no way to increase clock speed without causing chips to overheat.

In this week’s issue of the journal Science, MIT researchers and their colleagues at the University of Augsburg in Germany report the discovery of a new physical phenomenon that could yield transistors with greatly enhanced capacitance — a measure of the voltage required to move a charge. And that, in turn, could lead to the revival of clock speed as the measure of a computer’s power.”

MIT researchers and colleagues at the University of Augsburg, in Germany, investigated the curious electrical properties of a material produced by stacking layers of lanthanum aluminate on layers of strontium titanate.

The researchers’ experimental setup consisted of a sample of the lanthanum aluminate-strontium titanate composite, which looks like a slab of thick glass, with thin electrodes deposited on top of it.

See the full exciting article here.

From M.I.T. News: “Evolution, reversed”

Physicists’ study of evolution in bacteria shows that adaptations can be undone, but rarely.

Anne Trafton, MIT News Office

“Ever since Charles Darwin proposed his theory of evolution in 1859, scientists have wondered whether evolutionary adaptations can be reversed.

Answering that question has proved difficult, partly due to conflicting evidence. In 2003, scientists showed that some species of insects have gained, lost and regained wings over millions of years. But a few years later, a different team found that a protein that helps control cells’ stress responses could not evolve back to its original form.

Jeff Gore, assistant professor of physics at MIT, says the critical question to ask is not whether evolution is reversible, but under what circumstances it could be. ‘ It’s known that evolution can be irreversible. And we know that it’s possible to reverse evolution in some cases. So what you really want to know is: What fraction of the time is evolution reversible?’ he says.”

Graphic: Patrick Gillooly

See the full article here.

From M.I.T. news: “A new spin on superconductivity?”

Scientists produce a crystal that could help unlock the mystery of high-temperature superconductors.

Anne Trafton, MIT News Office
March 29, 2011

“MIT scientists have synthesized, for the first time, a crystal they believe to be a two-dimensional quantum spin liquid: a solid material whose atomic spins continue to have motion, even at absolute zero temperature.

The crystal, known as herbertsmithite, is part of a family of crystals called Zn-paratacamites, which were first discovered in 1906. Physicists started paying more attention to quantum spin liquids in 1987, when Nobel laureate Philip W. Anderson theorized that quantum spin liquid theory may relate to the phenomenon of high-temperature superconductivity, which allows materials to conduct electricity with no resistance at temperatures above 20 degrees Kelvin (-253 degrees Celsius).

MIT physicists grew this pure crystal of herbertsmithite in their laboratory. This sample is 7 mm long and weighs 0.2 grams.
Image: Tianheng Han

See the full article here.

From MIT News: “Explained: Quark gluon plasma”

This is old, but it is really good.

Anne Trafton, MIT News Office
June 9, 2010

http://web.mit.edu/newsoffice/2010/exp-quark-gluon-0609.html

“For a few millionths of a second after the Big Bang, the universe consisted of a hot soup of elementary particles called quarks and gluons. A few microseconds later, those particles began cooling to form protons and neutrons, the building blocks of matter.

Over the past decade, physicists around the world have been trying to re-create that soup, known as quark-gluon plasma (QGP), by slamming together nuclei of atoms with enough energy to produce trillion-degree temperatures.

‘If you’re interested in the properties of the microseconds-old universe, the best way to study it is not by building a telescope, it’s by building an accelerator,’ says Krishna Rajagopal, an MIT theoretical physicist who studies QGP.

Quarks and gluons, though they make up protons and neutrons, behave very differently from those heavier particles. Their interactions are governed by a theory known as quantum chromodynamics, developed in part by MIT professors Jerome Friedman and Frank Wilczek, who both won Nobel prizes for their work. However, the actual behavior of quarks and gluons is difficult to study because they are confined within heavier particles. The only place in the universe where QGP exists is inside high-speed accelerators, for the briefest flashes of time.

In 2005, scientists at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory reported creating QGP by smashing gold atoms together at nearly the speed of light. These collisions can produce temperatures up to 4 trillion degrees — 250,000 times warmer than the sun’s interior and hot enough to melt protons and neutrons into quarks and gluons.

The resulting super-hot, super-dense blob of matter, about a trillionth of a centimeter across, could give scientists new insights into the properties of the very early universe. So far, they have already made the surprising discovery that QGP is a nearly frictionless liquid, not the gas that physicists had expected.

By doing higher-energy collisions, scientists now hope to find out more about the properties of quark gluon plasma and whether it becomes gas-like at higher temperatures. They also want to delve further into the very surprising similarities that have been seen between QGP and ultracold gases (near absolute zero) that MIT’s Martin Zwierlein and others have created in the laboratory. Both substances are nearly frictionless, and theoretical physicists suspect that string theory may explain both phenomena, says Rajagopal.

At the Large Hadron Collider in Geneva, MIT faculty Gunther Roland, Wit Busza and Boleslaw Wyslouch are among the physicists planning to double the temperature achieved at Brookhaven, offering a glimpse of an even-earlier stage of the universe’s formation.”

A visualization of one of the first full-energy collisions between gold ions at Brookhaven Lab’s Relativistic Heavy Ion Collider, as captured by the Solenoidal Tracker At RHIC (STAR) detector. Image: Brookhaven National Laboratory

MIT News Office