Supersolid with Emergent SU(2) Symmetry

We present a model of a supersolid on a 2D triangular lattice with non-Abelian ground-state symmetry generators and examine the low-energy behavior using Bogoliubov theory. A mean-field phase diagram is found in terms of interaction parameters of the model and a region with an emergent SU(2) symmetry is identified at a phase boundary between a time-reversal (TR) symmetric and TR-broken supersolid. The enlarged degeneracy manifests itself via the acquisition of a quadratic Goldstone mode and the topological instability of global phase vortices. This latter point implies that such a supersolid is not expected to undergo a BKT superfluid transition. The zero-temperature superfluid fraction is calculated using linear response.