Field induced magnetic ordering transition in Kondo insulators

TL;DR

This paper investigates how a magnetic field induces a transition to an antiferromagnetically ordered insulating phase in 2D Kondo insulators, revealing the instability of the metallic phase due to Fermi surface nesting.

Contribution

It combines quantum Monte Carlo simulations and mean field analysis to elucidate the magnetic field-induced phase transition in Kondo insulators and the instability of the metallic phase.

Findings

Magnetic field induces antiferromagnetic insulating phase.

Metallic phase becomes unstable due to Fermi surface nesting.

Good agreement between Monte Carlo and mean field results.

Abstract

We study the 2D Kondo insulators in a uniform magnetic field using quantum Monte Carlo simulations of the particle-hole symmetric Kondo lattice model and a mean field analysis of the Periodic Anderson model. We find that the field induces a transition to an insulating, antiferromagnetically ordered phase with staggered moment in the plane perpendicular to the field. For fields in excess of the quasi-particle gap, corresponding to a metal in a simple band picture of the periodic Anderson model, we find that the metallic phase is unstable towards the spin density wave type ordering for any finite value of the interaction strength. This can be understood as a consequence of the perfect nesting of the particle and hole Fermi surfaces that emerge as the field closes the gap. We propose a phase diagram and investigate the quasi-particle and charge excitations in the magnetic field. We find good agreement between the mean-field and quantum Monte Carlo results.