Doping the Kane-Mele-Hubbard model: A Slave-Boson Approach

TL;DR

This paper investigates the phase diagram of the Kane-Mele-Hubbard model using a slave-boson mean-field approach, revealing a spin liquid phase and its evolution into superconductivity upon doping, with implications for strongly spin-orbit coupled systems.

Contribution

It introduces a slave-boson mean-field method to analyze the Kane-Mele-Hubbard model, identifying a spin liquid phase and its transition to superconductivity with doping.

Findings

Identification of a spin liquid phase at half-filling.

Superconductivity emerges upon doping the spin liquid.

Existence of an optimal doping level for superconductivity.

Abstract

We study the Kane-Mele-Hubbard model both at half-filling and away from half-filling using a slave-boson mean-field approach at zero temperature. We obtain a phase diagram at half-filling and discuss its connection to recent results from quantum Monte Carlo, slave-rotor, and $Z_2$ mean-field studies. In particular, we find a small window in parameter space where a spin liquid phase with gapped spin and charge excitations reside. Upon doping, we show the spin liquid state becomes a superconducting state by explicitly calculating the singlet pairing order parameters. Interestingly, we find an "optimal" doping for such superconductivity. Our work reveals some of the phenomenology associated with doping an interacting system with strong spin-orbit coupling.