Spin liquid ground state in a two dimensional non-frustrated spin model

TL;DR

This paper investigates a two-dimensional non-frustrated spin model, revealing a likely spin liquid ground state characterized by a finite spin gap and absence of order, using Green's Function Monte Carlo methods.

Contribution

It introduces a novel 2D spin model relevant for orbital degeneracy systems and demonstrates the existence of a spin liquid ground state through numerical analysis.

Findings

Finite spin gap observed

No evidence of magnetic or dimer order

Ground state likely a resonating valence bond spin liquid

Abstract

We consider an exchange model describing two isotropic spin-1/2 Heisenberg antiferromagnets coupled by a quartic term on the square lattice. The model is relevant for systems with orbital degeneracy and strong electron-vibron coupling in the large Hubbard repulsion limit, and is known to show a spin-Peierls-like dimerization in one dimension. In two dimensions we calculate energy gaps, susceptibilities, and correlation functions with a Green's Function Monte Carlo. We find a finite spin gap and no evidence of any kind of order. We conclude that the ground state is, most likely, a spin liquid of resonating valence bonds.