Dirac Kondo effect under magnetic catalysis

TL;DR

This paper introduces a mean-field theory for a novel Dirac Kondo effect that occurs under strong magnetic fields, highlighting the competition with chiral symmetry breaking and identifying a quantum critical point.

Contribution

It presents a new theoretical framework for the Dirac Kondo effect in systems without a Fermi surface, including finite-temperature analysis and potential for lattice simulations.

Findings

Identification of a Kondo condensate involving Dirac fermions and impurities

Discovery of a quantum critical point due to competition between Kondo effect and gap formation

Finite-temperature effects analyzed, with relevance to lattice simulations

Abstract

We develop a mean-field theory of a novel Kondo effect emerging in systems without a Fermi surface, which instead emerges under strong magnetic fields. We determine the magnitude of the Kondo condensate which is a particle pairing composed of conducting Dirac fermions and localized impurities. We focus on the competition between the Kondo effect and the energy gap formation that stems from the pairing among the Dirac fermions leading to the dynamical chiral symmetry breaking. We find that this competition induces a quantum critical point. We also investigate finite-temperature effects. This system at vanishing fermion density can be studied with Monte Carlo lattice simulations which do not suffer from the sign problem.