Physicists find signs of a time crystal

Yale physicists looked for a signature of a discrete time crystal within a crystal of monoammonium phosphate. Credit: Michael Marsland/Yale University

Yale physicists have uncovered hints of a time crystal—a form of matter that “ticks” when exposed to an electromagnetic pulse—in the last place they expected: a crystal you might find in a child’s toy.

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.

Scientists say that understanding time crystals may lead to improvements in atomic clocks, gyroscopes, and magnetometers, as well as aid in building potential quantum technologies. The U.S. Department of Defense recently announced a program to fund more research into time crystal systems.

Yale’s new findings are described in a pair of studies, one in Physical Review Letters and the other in Physical Review B. The studies represent the second known experiment observing a telltale signature for a discrete time crystal (DTC) in a solid. Previous experiments led to a flurry of media attention in the past year.

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