Valence bond spin liquid state in two-dimensional frustrated spin-1/2 Heisenberg antiferromagnets

TL;DR

This paper introduces a fermionic valence bond approach to describe a gapless valence bond spin liquid state in a two-dimensional frustrated J1-J2 Heisenberg antiferromagnet on a bipartite square lattice, predicting observable neutron scattering signatures.

Contribution

A novel SU(4) fermionic valence bond mean field theory for the J1-J2 model that captures a gapless spin liquid state interpolating between antiferromagnetic orders.

Findings

Identifies a gapless valence bond spin liquid state.

Predicts a sharp resonance peak in the dynamic structure factor.

Describes the state as stable in the strongly frustrated J2/J1 regime.

Abstract

Fermionic valence bond approach in terms of SU(4) representation is proposed to describe the $J_{1}-J_{2}$ frustrated Heisenberg antiferromagnetic (AF) model on a {\it bipartite} square lattice. A uniform mean field solution without breaking the translational and rotational symmetries describes a valence bond spin liquid state, interpolating the two different AF ordered states in the large $J_{1}$ and large $J_{2}$ limits, respectively. This novel spin liquid state is gapless with the vanishing density of states at the Fermi nodal points. Moreover, a sharp resonance peak in the dynamic structure factor is predicted for momenta ${\bf q}=(0,0)$ and $(\pi ,\pi)$ in the strongly frustrated limit $J_{2}/J_{1}\sim 1/2$, which can be checked by neutron scattering experiment.