Chiral tunneling of topological states: towards the efficient generation of spin current using spin-momentum locking

TL;DR

This paper demonstrates how chiral tunneling combined with spin-momentum locking in topological insulators can significantly amplify and filter spin currents, enabling efficient spintronic device functionalities.

Contribution

It introduces a novel mechanism leveraging chiral tunneling and spin-momentum locking to enhance spin current generation and control in topological insulators.

Findings

Spin current is amplified at the reflected end due to spin-momentum locking.

The spin to charge current ratio can reach approximately 20 and is tunable via gating.

Electrons transmitted through the junction are fully spin polarized.

Abstract

We show that the interplay between chiral tunneling and spin-momentum locking of helical surface states leads to spin amplification and filtering in a 3D Topological Insulator (TI). Chiral tunneling across a TI pn junction allows normally incident electrons to transmit, while the rest are reflected with their spins flipped due to spin-momentum locking. The net result is that the spin current is enhanced while the dissipative charge current is simultaneously suppressed, leading to an extremely large, gate tunable spin to charge current ratio (~20) at the reflected end. At the transmitted end, the ratio stays close to one and the electrons are completely spin polarized.