Spin-gap phase of a quantum spin system on a honeycomb lattice

TL;DR

This paper investigates the phase diagram of a frustrated and distorted quantum spin system on a honeycomb lattice, revealing a broad spin-gap phase and comparing it to square lattice models.

Contribution

The authors develop a novel transformation to a nonlinear sigma model that accurately captures the ground-state phases of the honeycomb lattice spin system.

Findings

The spin-gap phase spans a wide range of frustration and distortion regimes.

The spin-gap phase on the honeycomb lattice is larger than on the square lattice for spin-half systems.

The phase diagram includes both ordered antiferromagnetic and disordered spin-gap phases.

Abstract

We study a quantum spin system on a honeycomb lattice, when it includes frustration and distortion in antiferromagnetic (AF) exchange interactions. We transform the spin system onto a nonlinear sigma model (NLSM) in a new way preserving the original spin degrees of freedom. Assisted by a renormalization- group argument, the NLSM provides a ground-state phase diagram consisting of an ordered AF phase and a disordered spin-gap phase. The spin-gap phase extends from a strong frustration regime to a strong distortion regime, showing that the disordered ground states are essentially the same in both the regimes. In the spin-half case, the spin-gap phase for the spin system on a honeycomb lattice is larger than that for the J1-J2 model on a square lattice.