A Fractionalized Quantum Spin Hall Effect

TL;DR

This paper explores how electron correlations influence a 2D quantum spin Hall system, revealing a novel fractionalized phase where spinons carry spin without charge, expanding understanding of topological phases.

Contribution

It introduces a fractionalized quantum spin Hall phase in a Hubbard model on a bilayer honeycomb lattice, highlighting a new topological state beyond conventional phases.

Findings

Discovery of a fractionalized quantum spin Hall phase

Identification of a new topological state with spinons carrying spin only

Discussion of experimental signatures and fluctuation effects

Abstract

Effects of electron correlations on a two dimensional quantum spin Hall (QSH) system are studied. We examine possible phases of a generalized Hubbard model on a bilayer honeycomb lattice with a spin-orbit coupling and short range electron-electron repulsions at half filling, based on the slave rotor mean-field theory. Besides the conventional QSH phase and a broken-symmetry insulating phase, we find a new phase, a fractionalized quantum spin Hall phase, where the QSH effect arises for fractionalized spinons which carry only spin but not charge. Experimental manifestations of the exotic phase and effects of fluctuations beyond the saddle point approximation are also discussed.