One group at the University of Maryland lined up ten trapped ytterbium ions (ytterbium is just a chemical element) and shined them with periodic laser pulses to mostly, but not completely, flip the ions’ spins. The particles’ spin values snapped into place, completely flipping regardless. They continued flipping and all lining up at half the speed of the laser pulse. If the team altered the pulse a little bit, the ten ions kept with their same cycle, even though intuition says the time crystal’s periodic motion should eventually fall apart. Instead, they preferred to march at the beat of their own drum.
The Harvard group’s setup was a little different. They loaded the regular carbon lattice of a diamond with impurities in the form of nitrogen atoms—so many impurities that the diamond turned black. Their crystal also required a pulsing force, in this case a microwave field, and they also watched the impurities’ spins flip back and forth, snapping into place with their own lower frequency, a longer period. This caused the diamond to fluoresce… Their system was so complex that the theory doesn’t fully explain the behavior, said Soonwon Choi.
From: Scientists Finally Observed Time Crystals—But What the Hell Are They?
