Signatures of gapless fermionic spinons on a strip of the kagome Heisenberg antiferromagnet

TL;DR

This paper identifies a gapless quantum spin liquid phase with fermionic spinons in a quasi-1D kagome Heisenberg antiferromagnet, using advanced numerical methods to reveal a novel extended gapless phase with incommensurate correlations.

Contribution

It provides one of the first numerical demonstrations of emergent fermionic spinons in a simple SU(2) invariant Heisenberg model beyond 1D, revealing a new gapless quantum phase.

Findings

Extended gapless phase with central charge c=2

Power-law decaying correlations with incommensurate wave vectors

Interpretation as a marginal instability of a two-band spinon Fermi surface

Abstract

The search for exotic quantum spin liquid states in simple yet realistic spin models remains a central challenge in the field of frustrated quantum magnetism. Here we consider the canonical nearest-neighbor kagome Heisenberg antiferromagnet restricted to a quasi-1D strip consisting entirely of corner-sharing triangles. Using large-scale density matrix renormalization group calculations, we identify in this model an extended gapless quantum phase characterized by central charge $c=2$ and power-law decaying spin and bond-energy correlations which oscillate at tunably incommensurate wave vectors. We argue that this intriguing spin liquid phase can be understood as a marginal instability of a two-band spinon Fermi surface coupled to an emergent U(1) gauge field, an interpretation which we substantiate via bosonization analysis and Monte Carlo calculations on model Gutzwiller variational wave functions. Our results represent one of the first numerical demonstrations of emergent fermionic spinons in a simple SU(2) invariant nearest-neighbor Heisenberg model beyond the strictly 1D (Bethe chain) limit.