  Nonreciprocal nonequilibrium process are attracting growing interest in
sociology, animal behaviour, chemistry, and nanotechnology, and may have played
a role in the origin of life. It is less widely recognized, however, that in
open systems light can induce nonreciprocal predator-prey like forces between
nanoparticles. Such forces provide access to the continuous time crystal state
of matter, which has been demonstrated in a plasmonic metamaterial array of
nanowires wherein light triggers a spontaneous mobilization transition to the
robust oscillatory state, breaking time translation symmetry. Here, we report
on the first experimental study of the transient dynamics of light-induced
mobilization and demobilization in a time crystal. By analysing time resolved
phase trajectories of the system of nanowires, we show that the mobilization
transition is accompanied by breaking of continuous time translation symmetry
and ergodicity, and a decrease in the entropy of motion. This insight into the
transient dynamics of a nonreciprocity-driven time crystal is relevant to
optical timetronics, an information and communications technology paradigm
relying on the unique functionalities of time crystals, and applications of the
interacting nanowire oscillator platform to modelling a wide range of
nonreciprocal processes from many-body dynamics to the early stages of
matter-to-life transitions.
