Field induced quantum spin liquid with spinon Fermi surfaces in the Kitaev model

TL;DR

This paper investigates the ground state of the honeycomb Kitaev model under a perpendicular magnetic field, identifying a gapless quantum spin liquid with spinon Fermi surfaces and mapping its phase diagram.

Contribution

It provides a theoretical and numerical demonstration that an intermediate magnetic field induces a $U(1)$ quantum spin liquid with spinon Fermi surfaces in the Kitaev model, elucidating its phase transitions.

Findings

Identification of a $U(1)$ QSL with spinon Fermi surfaces

Mapping of the phase diagram under magnetic field and bond anisotropy

Characterization of continuous quantum phase transitions

Abstract

Recent experimental evidence for a field-induced quantum spin liquid (QSL) in $\alpha$-RuCl$_3$ calls for an understanding for the ground state of honeycomb Kitaev model under a magnetic field. In this work we address the nature of an enigmatic gapless paramagnetic phase in the antiferromagnetic Kitave model, under an intermediate magnetic field perpendicular to the plane. Combining theoretical and numerical efforts, we identify this gapless phase as a $U(1)$ QSL with spinon Fermi surfaces. We also reveal the nature of continuous quantum phase transitions involving this $U(1)$ QSL, and obtain a phase diagram of the Kitaev model as a function of bond anisotropy and perpendicular magnetic field.