A possible new form of ’supersolid’ matter

Frozen helium-4 behaves like a combination of solid and superfluid

Researchers at the Pennsylvania State University are announcing the possible discovery of an entirely new phase of matter: an ultra-cold, “supersolid” form of helium-4.

Writing in the 15 January 2004 issue of the journal Nature, Penn State physicist Moses H. W. Chan and his graduate student, Eun-Seong Kim, explain that their material is a solid in the sense that all its helium-4 atoms are frozen into a rigid crystal lattice, much like the atoms and molecules in a normal solid such as ice. The difference is that “frozen,” in this case, doesn’t mean “stationary.” Because helium-4 lattice is so very cold, less than one tenth of a degree above absolute zero, the laws of quantum uncertainty take over. In effect, the helium atoms start to behave as if they were both solid and fluid–at the same time. Under the right circumstances, in fact, some fraction of the helium atoms can begin to move through the lattice like a substance known as a “superfluid”: a liquid that moves with no friction whatsoever. Thus the name “supersolid.”

Chan and Kim’s work, which was funded by the National Science Foundation (NSF), is described in a Penn State press release posted on the EurekAlert site. That site has an embargo of 1 pm Eastern time, 14 January 2004. After that time, the release will also be available at http://www.science.psu.edu/alert/Chan1-2004.htm.

In addition, NSF has prepared an animation that illustrates the basics of Chan and Kim’s experimental setup, and the supersolid behavior they believe they have detected.

Program contact: Hollis Wickman, 703-292-4929, hwickman@nsf.gov.
Principal Investigator: Moses H.W. Chan, 814-863-2622, Mhc2@psu.edu.