If supersolidity exists, scientists thought, they should look for it in solid helium. With just two protons in its nucleus, a helium atom is relatively light.
The breakthrough came after John Goodkind of the University of California, San Diego reported that sound waves traveled in an unexpected manner through solid helium. Intrigued, Moses Chan of Pennsylvania State University in University Park decided to launch a new study of solid helium using a device called a torsional oscillator.
Yet when they filled their torsional oscillator with solid helium and spun the machine, they saw its period get shorter--presumably because some of the solid helium was becoming decoupled from the system instead of rotating with it.
1908: Dutch scientists produced liquid and solid helium
for the first time
6 Dutch scientists produced solid helium
on Leap Day 1908.
In their current experiment, they observed the same superfluid-like behavior in samples of bulk solid helium without any confining matrix.
"Our current experiments with bulk solid helium indicate that the superfluid-like behavior we observed is an intrinsic property of the solid--not the result of confinement in any particular porous medium and not a consequence of the large surface area that accompanies a porous host," Chan explains.
Adding even more pressure caused the oxygen and helium to solidify, resulting in 100-micrometer-long [epsilon]-oxygen crystals that were surrounded by solid helium
and therefore protected from shear stresses.
To explore the behavior of solid helium, the researchers placed inside the oscillator's bob a porous glass disk the diameter of a dime.
Solid helium's superfluidity indicates that a so-called Bose-Einstein condensate forms within the material.
In the 1980s, scientists searched for such facets in lead, gold, and solid helium
. They came up empty-handed, however, observing no more than a half-dozen different facet types, none shallowly oriented.
A report in the April 3, 1972 Physical Review Letters described the discovery of a new phase of solid helium
(SN: 4/15/72, p.