Pristine Mott Insulator from an Exactly Solvable Spin-1/2 Kitaev Model

TL;DR

This paper introduces an exactly solvable spin-1/2 model on a 2D lattice that exhibits a pristine Mott insulator state with gapless spinons, topological degeneracy, and non-Abelian anyons when symmetry is broken.

Contribution

It presents a novel exactly solvable model with time reversal invariance that reveals a quantum spin liquid with unique topological and excitation properties.

Findings

Ground state is an algebraic quantum spin liquid.

Spinon excitations are gapless with Dirac points.

Breaking time reversal symmetry induces non-Abelian statistics.

Abstract

We propose an exactly solvable quantum spin-1/2 model with time reversal invariance on a two dimensional brick-wall lattice, where each unit cell consists of three sites. We find that the ground states are algebraic quantum spin liquid states. The spinon excitations are gapless and the energy dispersion is linear around two Dirac points. The ground states are of three-fold topological degeneracy on a torus. Breaking the time reversal symmetry opens a bulk energy gap and the $Z_2$ vortices obey non-Abelian statistics.