Theory of a competitive spin liquid state for weak Mott insulators on the triangular lattice

TL;DR

This paper introduces a new quantum spin liquid state for weak Mott insulators on the triangular lattice, explaining experimental observations with a symmetric, gapless, quadratic band touching state supported by variational Monte Carlo calculations.

Contribution

It proposes a novel symmetric spin liquid state with quadratic band touching, providing a theoretical framework for understanding experimental properties of organic spin liquid materials.

Findings

The proposed state preserves all symmetries of the system.

It exhibits a gapless excitation spectrum with quadratic bands.

Variational Monte Carlo shows this state has competitive energy in relevant models.

Abstract

We propose a novel quantum spin liquid state that can explain many of the intriguing experimental properties of the low-temperature phase of the organic spin liquid candidate materials. This state of paired fermionic spinons preserves all symmetries of the system, and it has a gapless excitation spectrum with quadratic bands that touch at momentum ~ k = 0. This quadratic band touching is protected by the symmetry of the system. Using variational Monte Carlo techniques, we show that this state has highly competitive energy in the triangular lattice Heisenberg model supplemented with a realistically large ring-exchange term.