Gapless chiral spin liquid in a kagome Heisenberg model

TL;DR

This paper classifies chiral spin liquids on the kagome lattice, proposes a gapless chiral spin liquid phase in kapellasite, and compares variational wave functions to experimental data.

Contribution

It provides a comprehensive classification of chiral spin liquids on the kagome lattice and predicts a gapless chiral spin liquid phase in kapellasite based on variational calculations.

Findings

Kapellasite likely exhibits a gapless chiral spin liquid phase.

The phase inherits properties from one-dimensional antiferromagnetic chains.

The study compares energies of various variational wave functions.

Abstract

Motivated by recent experiments on the Heisenberg S=1/2 quantum spin liquid candidate material kapellasite, we classify all possible chiral (time-reversal symmetry breaking) spin liquids with fermionic spinons on the kagome lattice. We obtain the phase diagram for the physically relevant extended Heisenberg model, comparing the energies of a wide range of microscopic variational wave functions. We propose that, at low temperature, kapellasite exhibits a gapless chiral spin liquid phase with spinon Fermi surfaces. This two-dimensional state inherits many properties of the nearby one-dimensional phase of decoupled anti-ferromagnetic spin chains, but also shows some remarkable differences. We discuss the spin structure factors and other physical properties.