Spin Generation Via Bulk Spin Current in Three Dimensional Topological Insulators

TL;DR

This paper introduces a novel bulk-mediated spin generation mechanism in three-dimensional topological insulators, where an electric field induces a transverse pure spin current through the bulk, enhancing spin transport between surfaces.

Contribution

It reveals a bulk spin generation process in 3D topological insulators, distinct from surface-only models, and demonstrates how disorder can enhance spin efficiency and conductivity.

Findings

Bulk spin current transports spins between surfaces

Disorder extends spin relaxation time via Dyakonov-Perel mechanism

Spin generation is unique to 3D topological insulators, not present in graphene

Abstract

To date, spin generation in three-dimensional topological insulators is primarily modeled as a single-surface phenomenon, attributed to the momentum-spin locking on each individual surface. In this article we propose a mechanism of spin generation where the role of the insulating yet topologically non-trivial bulk becomes explicit: an external electric field creates a transverse pure spin current through the bulk of a three-dimensional topological insulator, which transports spins between the top and bottom surfaces. Under sufficiently high surface disorder, the spin relaxation time can be extended via the Dyakonov-Perel mechanism. Consequently both the spin generation efficiency and surface conductivity are largely enhanced. Numerical simulation confirms that this spin generation mechanism originates from the unique topological connection of the top and bottom surfaces and is absent in other two dimensional systems such as graphene, even though they possess a similar Dirac cone-type dispersion.