Yale Physicists Find Signs of a Time Crystal

Yale physicists have uncovered hints of a time crystal, a form of matter that "ticks" when exposed to an electromagnetic pulse, in a child's toy. The discovery means there are now new puzzles to solve, in terms of how time crystals form in the first place. Yale News reports: Ordinary crystals such as salt or quartz are examples of three-dimensional, ordered spatial crystals. Their atoms are arranged in a repeating system, something scientists have known for a century. Time crystals, first identified in 2016, are different. Their atoms spin periodically, first in one direction and then in another, as a pulsating force is used to flip them. That's the "ticking." In addition, the ticking in a time crystal is locked at a particular frequency, even when the pulse flips are imperfect.

Monoammonium phosphate (MAP) crystals are considered so easy to grow that they are sometimes included in crystal growing kits aimed at youngsters. It would be unusual to find a time crystal signature inside a MAP crystal, [Yale Physics professor Sean Barrett] explained, because time crystals were thought to form in crystals with more internal "disorder." The researchers used nuclear magnetic resonance (NMR) to look for a DTC signature -- and quickly found it. Another unexpected thing happened, as well. "We realized that just finding the DTC signature didn't necessarily prove that the system had a quantum memory of how it came to be," said Yale graduate student Robert Blum, a co-author on the studies. "This spurred us to try a time crystal 'echo,' which revealed the hidden coherence, or quantum order, within the system," added Rovny, also a Yale graduate student and lead author of the studies. The findings are described in a pair of studies, one in the journal Physical Review Letters and the other in the journal Physical Review B.