* Astronomy

Frozen helium-4 may be an unusual 'superglass'
Frozen helium-4 that flows without friction may be a superglass rather than a crystalline supersolid, according to Cornell researchers.

When helium is cooled to around 4 degrees above absolute zero, it turns liquid. Make it a couple of degrees cooler, and it becomes a "superfluid" that flows without resistance from its container, just as electrons flow without resistance in a superconductor.
Now pressurise the helium to about 50 atmospheres until it solidifies, and then cool it a lot more to about two-tenths of a degree above absolute zero, and it becomes -- well, there's a lot of argument about what it is. Perhaps a supersolid, or a solid with some superfluid moving through it.
In fact, it may be a superglass, report J.C. Séamus Davis, the James Gilbert White Distinguished Professor in the Physical Sciences at Cornell and colleagues in the May 1 issue of the journal Science.

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Physicists at the University of Alberta have made a major advance in the understanding of what appears to be a new state of matter.
Working in the highly specialized field of quantum fluids and solids, professor John Beamish, chair of the Department of Physics, and PhD student James Day, report their findings in a paper published in the science journal Nature today. Beamish and Day are the only researchers in Canada conducting experimental research in this area of fundamental physics.
At very low temperatures, helium gas turns into a liquid. Put under extreme pressure the liquid turns into a solid. Physicists have been manipulating solid helium so they can study its unusual behaviour.
In 2004, a research team at Penn State University, led by Moses Chan, startled the physics world when it announced that it may have discovered an entirely new state of matter - supersolidity. The team made its discovery by cooling solid helium to an extremely low temperature and oscillating the material at different speeds. They found that the particles behaved in a way not seen before, which suggested it might show the "perpetual flow" seen in superfluids like liquid helium.
Day and Beamish have taken this research a different direction. In an experiment not done before, they cooled the solid helium and manipulated the material another way - by shearing it elastically. In doing so, they found that the solid behaved in an entirely new and unexpected way - it became much stiffer at the lowest temperatures.

"The experimental results from the University of Alberta are remarkable. This is an important breakthrough, since the original discovery" - Moses Chan.

Other physicists around the world are also studying the implications. Through this discovery, Beamish and Day have significantly added to the body of knowledge about the fundamental states of matter allowed by nature.

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The mysterious saga of "supersolid" helium continues this week. If you recall, there were some new results a little while back showing that the effect depends on disorder in the samples, followed by neutron scattering studies that didn't show the expected distribution of states in the sample. These results suggest that something else is going on in these samples, and the explanation of the observed effects isn't all that simple.

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