Influence of Rashba spin-orbit coupling on the Kondo effect

TL;DR

This paper investigates how Rashba spin-orbit coupling influences the Kondo effect in a 2D electron gas, revealing conditions for exponential T_K enhancement and unique spin correlations, with implications for manipulating magnetic impurities.

Contribution

It provides a detailed analysis of the Kondo effect under Rashba spin-orbit interaction using numerical renormalization group methods, highlighting new regimes and universal scaling behaviors.

Findings

Weak T_K variation with Rashba coupling at fixed Fermi energy

Exponential T_K enhancement in low band filling regimes with increasing lpha

Universal impurity angular momentum scaling with Zeeman energy ratio

Abstract

An Anderson model for a magnetic impurity in a two-dimensional electron gas with bulk Rashba spin-orbit interaction is solved using the numerical renormalization group under two different experimental scenarios. For a fixed Fermi energy, the Kondo temperature T_K varies weakly with Rashba coupling \alpha, as reported previously. If instead the band filling is low and held constant, increasing \alpha can drive the system into a helical regime with exponential enhancement of T_K. Under either scenario, thermodynamic properties at low temperatures T exhibit the same dependences on T/T_K as are found for \alpha = 0. Unlike the conventional Kondo effect, however, the impurity exhibits static spin correlations with conduction electrons of nonzero orbital angular momentum about the impurity site. We also consider a magnetic field that Zeeman splits the conduction band but not the impurity level, an effective picture that arises under a proposed route to access the helical regime in a driven system. The impurity contribution to the system's ground-state angular momentum is found to be a universal function of the ratio of the Zeeman energy to a temperature scale that is not T_K (as would be the case in a magnetic field that couples directly to the impurity spin), but rather is proportional to T_K divided by the impurity hybridization width. This universal scaling is explained via a perturbative treatment of field-induced changes in the electronic density of states.