Crystals feature an atomic lattice structure repeated in space. Time crystals repeat their atomic structure in time.
Norman Yao, a physicist at the University of California, Berkeley, laid out the theoretical blueprint for time crystals in a paper published last week in the journal Physical Review Letters.
The new form of matter isn’t just hypothetical. Two teams of scientists, at the University of Maryland and Harvard University, have created time crystals in the lab. Both have described their successes in forthcoming papers.
Time crystals reveal their temporal repetition because they’re intermittently kicked, making them jiggle like Jell-O. They behave this way, researchers explain, because they are inherently unstable, unable to establish motionless equilibrium.
“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,” Yao said in a news release. “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.”
Researchers at Maryland created their time crystal using 10 ytterbium ions. Scientists excite the ions’ electrons by continuously hitting the crystal with a laser, creating a mini magnetic field. A second pulsing laser causes the spin rates of the electrons to flip. Together the lasers create a sort of pendulum of electrons, their spin rates interacting in a perfect repetitive pattern — like a crystal.
Importantly, the spin flipping pattern occurs at a rate unique from the lasers driving the action. The repetitive non-equilibrium breaks time symmetry.
“Wouldn’t it be super weird if you jiggled the Jell-O and found that somehow it responded at a different period?” Yao said. “But that is the essence of the time crystal. You have some periodic driver that has a period T, but the system somehow synchronizes so that you observe the system oscillating with a period that is larger than T.”
Harvard researchers materialized Yao’s theory using tightly packed nitrogen vacancy centers — the holes left when nitrogen atoms are systematically stolen — in diamonds.
Researchers aren’t yet sure what applicable value time crystals might offer, but they could potentially be used in quantum computing systems, as they mimic the qubit information bits.
Filed Under: Materials • advanced