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“This is a new phase of matter, period, but it is also really cool because it is one of the first examples of non-equilibrium matter,” said lead researcher Norman Yao from the University of California, Berkeley. “For the last half-century, we have been exploring equilibrium matter, like metals and insulators. We are just now starting to explore a whole new landscape of non-equilibrium matter.”
|Chris Monroe, University of Maryland|
Because the spins of all the atoms were entangled, the atoms settled into a stable, repetitive pattern of spin flipping that defines a crystal.
That was normal enough, but to become a time crystal, the system had to break time symmetry. And observing the ytterbium atom conga line, the researchers noticed it was doing something odd. The two lasers that were periodically nudging the ytterbium atoms were producing a repetition in the system at twice the period of the nudges, something that couldn’t occur in a normal system.
“Wouldn’t it be super weird if you jiggled the Jell-O and found that somehow it responded at a different period?” said Yao. “But that is the essence of the time crystal. You have some periodic driver that has a period ‘T’, but the system somehow synchronises so that you observe the system oscillating with a period that is larger than ‘T’.”
Under different magnetic fields and laser pulsing, the time crystal would then change phase, just like an ice cube melting.