Multinode quantum spin liquids in extended Kitaev honeycomb models: the view from variational Monte Carlo

TL;DR

This paper uses variational Monte Carlo methods to identify and classify multinode quantum spin liquids in extended Kitaev honeycomb models, revealing their topological properties and potential for experimental realization.

Contribution

It introduces a PSG-guided VMC framework for classifying multinode QSLs, including their symmetry, topology, and relation to experimental materials.

Findings

Discovery of multinode QSLs with Z2 gauge structure

Identification of symmetry-protected Majorana cones

Proposal of a classification framework for nodal QSLs

Abstract

We discuss the discovery by variational Monte Carlo (VMC) methods of a series of multinode quantum spin liquids (QSLs) in extended Kitaev models on the honeycomb lattice. Like the gapless Kitaev spin liquid with its two nodes at K and K$^\prime$, these multinode QSLs are characterized by an emergent Z$_2$ gauge structure and a discrete number of symmetry-protected Majorana cones in their low-energy excitation spectrum. Because the cones are gapped by weak magnetic fields, nonzero Chern numbers are obtained and the ground state becomes one of many possible Abelian or non-Abelian chiral spin liquids. Here we focus on the projective symmetry group (PSG)-guided VMC approach to the Kitaev model with various symmetry-allowed extended interactions. Based on the VMC phase diagrams of these models, we propose a framework for the classification of nodal QSLs that includes the PSG, the chiralities of the cones, and the way in which the cones are symmetry-related. At present, the known candidate Kitaev materials seem to lie outside the parameter regimes of the multinode QSL phases. However, with more than 100 Z$_2$ PSGs for spin-orbit-coupled states on the honeycomb lattice, we anticipate that more than one multinode QSL will be realized experimentally in future work.