May 18, 2011 13:47 GMT  ·  By
When liquid helium is cooled down to the lambda point at 2.2K the liquid for a brief moment boils up violently. After boiling ceases, the transition from the normal phase to the superfluid phase is complete
   When liquid helium is cooled down to the lambda point at 2.2K the liquid for a brief moment boils up violently. After boiling ceases, the transition from the normal phase to the superfluid phase is complete

Studies conducted at the US Department of Energy's (DOE) Los Alamos National Laboratory (LANL) reveal that helium-4 may in fact not enter a weird state of matter known as “supersolid” when cooled down to extremely low temperatures.

The idea stating that this happens has been proposed a long time ago, but thus far no one was able to conclusively demonstrate that this is indeed the case. On the other hand, the LANL team demonstrated that the transition does not take place.

Experts at the DOE lab published all the details of their work in the latest issue of the top journal Science. LANL researchers Alexander Balatsky and Matthias Graf conducted this work together with Cornell University physicist J.C. Séamus Davis.

According to analysts, there is a considerable chance that the international community will have a hard time accepting the new study, given that it goes up against a 40-years-old proposal. A supersolid is a state of matter in which an element is both liquid and solid at the same time.

Conceivably, this only happened for helium-4 when it was cooled at temperatures nearing absolute zero. However, the LANL / Cornell group came up with an entirely different explanation for the observations made in previous studies.

The reason why physicists believed that helium-4 turns into a supersolid until now is the weird behavior the material exhibits when cooled. Below minus 452 degrees Fahrenheit it can become a liquid without viscosity that can flow unhampered by friction – a superliquid.

When experts applied pressure on the ultra-cooled helium-4, they observe the formation of a lattice, which indicates the presence of a solid. What experts proposed until now is that the solid moved in the same frictionless manner as a superliquid, which would translate into a supersolid.

But researchers now suggest that the old readings were hampered by the inability to think about other potential explanations. They say that the previous conclusions are based on readings indicating that, at some point, oscillation speeds fluctuate in helium-4 that is moved in a special apparatus.

These evidence were interpreted as signifying that some of the helium had become solid, but moved frictionless with respect to the rest of the material. But now experts say that the gradual “freezing out” of imperfections within the helium-4 lattice may have been responsible for the data.

“While this experiment does not definitively rule out the possibility of the formation of a supersolid in helium-4, the fact that we have provided a reasonable alternative explanation for the observed behavior in earlier experiments weakens the argument that what was being seen was a phase change to a supersolid,” Balatsky explains.