Imagine an object that moves rhythmically, oscillating perpetually, without requiring external energy and never stopping. Although it sounds like science fiction or an impossible perpetual motion machine, this is the fundamental concept behind time crystals, one of the most exotic and fascinating phases of matter recently discovered. Unlike ordinary crystals, whose structure repeats in space (like the atomic lattice of a diamond), time crystals have a structure that repeats periodically in time. That is, their ground state, their lowest energy configuration, is not static, but moves and oscillates in a regular, constant pattern. This property is surprising, since systems in their ground state should be static to conserve energy. The key to their existence lies in breaking time-translation symmetry, one of the most fundamental laws of physics. A time crystal breaks this symmetry spontaneously: although the rules governing it are constant, its intrinsic behavior is not, manifesting as a rhythmic oscillation that persists even in its lowest energy state. The existence of time crystals was theoretically proposed by physicist Frank Wilczek in 2012 and experimentally confirmed in 2016 by teams from the University of Maryland and Harvard, using quantum systems such as trapped-ion chains. Although still in the early stages of research, they open doors to new understandings of quantum physics and could have future applications in quantum computers or extremely precise time sensors.
Source: Scientific American, Nature Physics, Physical Review Letters
