“Imagine you have an orchestra together, but everyone is playing their own tune, until they begin to follow a conductor. In a normal solid, every atom has its own behavior until very close to absolute zero. Then quantum mechanics takes over and dictates everyone to play the same tune.”
oscillator
That’s physics professor Moses Chan’s musical metaphor for his discovery that atoms in a solid can condense into what he likes to call “one giant atom,” a new phase of matter called a supersolid. Together with post-doctoral associate Eun-Seong Kim, Chan found that when a particular isotope of helium gas has frozen into a crystal at a fraction of a degree above absolute zero, part of it exhibits a property only seen before in superfluids: no friction.
To understand frictionless flow, says Chan, think of a bunch of kids sitting on a spinning merry-go-round. Normally, the more kids on the merry-go-round, the harder it is to stop the movement and reverse its direction. Chan and Kim set up an oscillator that spins back and forth like a merry-go-round shifting direction. They found that helium crystals in a normal solid state behaved as expected, with each additional bit of crystal adding to the mass of the “merry-go-round” and increasing the resistance.
However when those same crystals are frozen below 0.2 degrees Kelvin, something unexpected happens: one percent of the solid helium begins to flow without resistance. “It’s as if a portion of the kids on that merry-go-round are sitting on perfectly smooth ball bearings, unaffected by the merry-go-round sliding back and forth underneath them,” explains Chan. This allows the crystal to oscillate faster, as if the crystal has suddenly become lighter?or the kids have lost weight in mid-spin. Chan and Kim knew that the matter had not been lost because the missing mass re-materialized with the slightest rise in temperature, and the oscillation slowed back down to normal.