Nonequilibrium selection of magnetic order in driven triangular XY antiferromagnet

Abstract

We show that a weak periodic drive removes the accidental degeneracy in the ground state of the XY antiferromagnet on the triangular lattice in a uniform static magnetic field. The underlying mechanism involves adding a small periodically modulated component to the magnetic field, which influences finite-frequency modes to generate an effective potential for the accidental pseudo-Goldstone mode. This selection can be arranged to compete with the degeneracy lifting via the thermal order by disorder mechanism. This yields a non-equilibrium phase transition as the relative strength of the two mechanisms is tuned by varying temperature. This proposal may be amenable to experimental realization, in particular as applying the field is noninvasive, and no complex bath engineering is required.