Pseudospin-valve effect on transport in junctions of three-dimensional topological insulator surfaces

TL;DR

This paper demonstrates that the surface states of 3D topological insulators act like ferromagnetic half metals with a pseudospin polarization, leading to a spin-valve effect in tunneling conductance that is robust against various surface potentials.

Contribution

It introduces the pseudospin-valve effect in 3D topological insulator surfaces and analyzes its robustness against surface potentials.

Findings

Surface states behave as half metals with pseudospin polarization.

Tunneling conductance exhibits spin-valve-like behavior.

Effect remains stable under various surface potentials.

Abstract

We show that the surface states of pristine 3D topological insulators (TIs) are analogs of ferromagnetic half metals due to complete polarization of an emergent momentum independent pseudospin (SU(2)) degree of freedom on the surface. To put this claim on firm footing, we present results for TI surfaces perpendicular to the crystal growth axis, which clearly show that the tunneling conductance between two such TI surfaces of the same TI material is dominated by this half metallic behavior leading to physics reminiscent of a spin-valve. Further using the generalized tunnel magnetoresistance derived in this work we also study the tunneling current between arbitrary TI surfaces. We also perform a comprehensive study of the effect of all possible surface potentials allowed by time reversal symmetry on this spin-valve effect and show that it is robust against most of such potentials.