Researchers create a supersolid

Researchers in the United States think they have found a new state of matter - a supersolid.

If their findings are correct, this state is deeply bizarre. Although it is a crystalline solid, it can ‘flow’ like the most slippery liquid imaginable - in fact, like a liquid with no viscosity.

It is a bit hard to imagine the importance of such a finding, but I would guess that in the future this substance may be used as some type of superconductor, perhaps in a supercomputer type of application. It looks as though this supersolid exists only at near absolute zero temperatures and if it could be used it would be ideal in keeping microchips cool. I’m sure that we won’t see anything like it for years to come.

Solid helium itself is a fairly weird substance. At very low temperatures, the behaviour of helium atoms is dictated by quantum mechanics, and this prevents helium from freezing at all, no matter how cold it is, unless it is pressurized to at least 25 atmospheres. The ‘quantum solid’ that results is very loose - unlike most frozen solids it can be squeezed like rubber, and the regular crystal lattice of atoms is full of gaps, called vacancies, that move about.

When liquid helium becomes a superfluid, the laws of quantum mechanics make all the atoms move coherently, like a regiment of soldiers. This is why flow in a superfluid, once started, cannot easily be stopped.

In supersolid helium, all of the vacancies in the crystal likewise start to move coherently, which means that waves can progress through the lattice.

The onset of this coherent motion is called Bose-Einstein condensation. In superconductors, Bose-Einstein condensation of electrons at low temperatures allows electrical current to pass with no resistance. Since 1995, Bose-Einstein condensation of atoms has been seen in a variety of ultracold gases.

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