Mott scattering at the interface between a metal and a topological insulator

TL;DR

This paper analyzes spin-active scattering at a metal-topological insulator interface, revealing a critical angle for complete spin flip and the evolution of interface states, with implications for spintronics.

Contribution

It provides a detailed calculation of the scattering matrix and local spectrum, highlighting the critical incident angle and the nature of interface states in topological insulators.

Findings

Existence of a critical incident angle with 100% spin flip reflection

The interface spectrum features a Dirac cone in tunneling limit

Evolution from Dirac cone to metal-induced gap states with contact quality

Abstract

We compute the spin-active scattering matrix and the local spectrum at the interface between a metal and a three-dimensional topological band insulator. We show that there exists a critical incident angle at which complete (100%) spin flip reflection occurs and the spin rotation angle jumps by $\pi$. We discuss the origin of this phenomena, and systematically study the dependence of spin-flip and spin-conserving scattering amplitudes on the interface transparency and metal Fermi surface parameters. The interface spectrum contains a well-defined Dirac cone in the tunneling limit, and smoothly evolves into a continuum of metal induced gap states for good contacts. We also investigate the complex band structure of Bi$_2$Se$_3$.