Kondo effect under arbitrary spin-momentum locking

TL;DR

This paper investigates how arbitrary spin-momentum locking in Weyl-type electrons influences the Kondo effect, deriving a formula for the Kondo temperature that depends on the average spin over the Fermi surface.

Contribution

It generalizes the understanding of the Kondo effect to systems with arbitrary spin-momentum locking, providing a simple formula for the Kondo temperature based on the Fermi surface spin average.

Findings

Kondo temperature depends on the average spin over the Fermi surface.

Kondo temperature vanishes when the Fermi surface spin is fully polarized.

Spin-momentum locking can suppress the Kondo effect.

Abstract

The Kondo effect originates from the spin exchange scattering of itinerant electrons with a localized magnetic impurity. Here, we consider generalization of Weyl-type electrons with their spin locked on a spherical Fermi surface in an arbitrary way and study how such spin-momentum locking affects the Kondo effect. After introducing a suitable model Hamiltonian, a simple formula for the Kondo temperature is derived with the second-order perturbation theory, which proves to depend only on the spin averaged over the Fermi surface. In particular, the Kondo temperature is unaffected as long as the average spin vanishes, but decreases as the average spin increases in its magnitude, and eventually vanishes when the spin is completely polarized on the Fermi surface, illuminating the role of spin-momentum locking in the Kondo effect.