Discrete time crystal made of topological edge magnons in Kagome ferromagnet

We report the emergence of time-crystalline behavior in the π-Berry
phase protected edge states of a Heisenberg ferromagnet on the Kagome
lattice in the presence of an external driving field. The magnon
amplification due to the external field spontaneously breaks the discrete
time translational symmetry, resulting in a discrete time crystal with a
period that is twice that of the applied EM field. We discuss the nature
of the time crystalline edge states and their stability against various
perturbations that are expected in real quantum magnets. We propose an
experimental signature to unambiguously detect the time crystalline
behavior and identify two recently discovered quasi-2D magnets as
potential hosts. We present a first-of-its-kind realization of time
crystals at topological edge states, which can be generalized and
extrapolated to other bosonic quasi-particle systems that exhibit
parametric pumping and topological edge states.