Emergent Chiral Spin State in the Mott Phase of a Bosonic Kane-Mele-Hubbard Model

TL;DR

This paper proposes realizing a chiral spin state in a bosonic Kane-Mele-Hubbard model using ultra-cold atoms, revealing an emergent chiral phase with broken symmetries in the Mott regime.

Contribution

It introduces a new experimental approach to realize chiral spin liquids via the bosonic Kane-Mele-Hubbard model and characterizes its magnetic properties and emergent phases.

Findings

Discovery of an emergent chiral spin state in the Mott phase.

The chiral phase breaks time-reversal and parity symmetry.

The phase is not topologically ordered, with zero Chern number.

Abstract

Recently, the frustrated XY model for spins-1/2 on the honeycomb lattice has attracted a lot of attention in relation with the possibility to realize a chiral spin liquid state. This model is relevant to the physics of some quantum magnets. Using the flexibility of ultra-cold atoms setups, we propose an alternative way to realize this model through the Mott regime of the bosonic Kane-Mele-Hubbard model. The phase diagram of this model is derived using the bosonic dynamical mean-field theory. Focussing on the Mott phase, we investigate its magnetic properties as a function of frustration. We do find an emergent chiral spin state in the intermediate frustration regime. Using exact diagonalization we study more closely the physics of the effective frustrated XY model and the properties of the chiral spin state. This gapped phase displays a chiral order, breaking time-reversal and parity symmetry, but is not topologically ordered (the Chern number is zero).