Single Magnetic Impurity in Tilted Dirac Surface States

TL;DR

This paper investigates how tilting in Dirac surface states affects Kondo screening of magnetic impurities, revealing critical tilting effects on binding energy and anisotropic spin correlations.

Contribution

It introduces a variational approach to analyze the impact of tilt on Kondo physics in Dirac materials, highlighting the role of tilting in binding energy and spin correlations.

Findings

Critical tilting affects binding energy.

Tilt increases density of states at Fermi surface.

Spin-spin correlations are strongly anisotropic.

Abstract

We utilize variational method to investigate the Kondo screening of a spin-1/2 magnetic impurity in tilted Dirac surface states with the Dirac cone tilted along the $k_y$-axis. We mainly study about the effect of the tilting term on the binding energy and the spin-spin correlation between magnetic impurity and conduction electrons, and compare the results with the counterparts in a two dimensional helical metal. The binding energy has a critical value while the Dirac cone is slightly tilted. However, as the tilting term increases, the density of states around the Fermi surface becomes significant, such that the impurity and the host material always favor a bound state. The diagonal and the off-diagonal terms of the spin-spin correlation between the magnetic impurity and conduction electrons are also studied. Due to the spin-orbit coupling and the tilting of the spectra, various components of spin-spin correlation show very strong anisotropy in coordinate space, and are of power-law decay with respect to the spatial displacements.