Chiral spin liquids on the kagome Lattice

TL;DR

This paper investigates how various perturbations like chirality, Dzyaloshinski-Moriya, and ring-exchange terms can induce chiral spin liquids in the kagome lattice Heisenberg antiferromagnet using a flux attachment transformation.

Contribution

It demonstrates that specific perturbations can stabilize chiral spin liquids on the kagome lattice, providing a theoretical framework for their realization.

Findings

Chirality term induces a chiral spin liquid with spin Hall conductance 1/2.

Dzyaloshinski-Moriya interaction can lead to chiral spin liquids if not too strong.

Ring-exchange interactions can trigger phase transitions into chiral spin liquids.

Abstract

We study the nearest neighbor $XXZ$ Heisenberg quantum antiferromagnet on the kagome lattice. Here we consider the effects of several perturbations: a) a chirality term, b) a Dzyaloshinski-Moriya term, and c) a ring-exchange type term on the bowties of the kagome lattice, and inquire if they can suppport chiral spin liquids as ground states. The method used to study these Hamiltonians is a flux attachment transformation that maps the spins on the lattice to fermions coupled to a Chern-Simons gauge field on the kagome lattice. This transformation requires us to consistently define a Chern-Simons term on the kagome lattice. We find that the chirality term leads to a chiral spin liquid even in the absence of an uniform magnetic field, with an effective spin Hall conductance of $\sxy = \frac{1}{2}$ in the regime of $XY$ anisotropy. The Dzyaloshinkii-Moriya term also leads a similar chiral spin liquid but only when this term is not too strong. An external magnetic field also has the possibility of giving rise to additional plateaus which also behave like chiral spin liquids in the $XY$ regime. Finally, we consider the effects of a ring-exchange term and find that, provided its coupling constant is large enough, it may trigger a phase transition into a chiral spin liquid by the spontaneous breaking of time-reversal invariance.