Ideal two-dimensional electron systems with a giant Rashba-type spin splitting in real materials: surfaces of bismuth tellurohalides

TL;DR

This paper reports the discovery of giant Rashba-type spin splitting in 2D electron systems on bismuth tellurohalide surfaces, promising for spintronic device applications due to large spin-orbit interaction effects.

Contribution

It demonstrates the existence of a giant Rashba effect in 2D electron systems on tellurium-terminated surfaces of bismuth tellurohalides, especially BiTeCl, which was not previously known.

Findings

Giant Rashba spin splitting observed in BiTeCl surface states

Isotropic metallic surface-state band with deep Gamma-point energy

Substantial spin asymmetry in quasiparticle mean free paths

Abstract

Spintronics is aimed at active controlling and manipulating the spin degrees of freedom in semiconductor devices. A promising way to achieve this goal is to make use of the tunable Rashba effect that relies on the spin-orbit interaction (SOI) in a two-dimensional (2D) electron system immersed in an inversion-asymmetric environment. The SOI induced spin-splitting of the 2D-electron state provides a basis for many theoretically proposed spintronic devices. However, the lack of semiconductors with large Rashba effect hinders realization of these devices in actual practice. Here we report on a giant Rashba-type spin splitting in 2D electron systems which reside at tellurium-terminated surfaces of bismuth tellurohalides. Among these semiconductors, BiTeCl stands out for its isotropic metallic surface-state band with the Gamma-point energy lying deep inside the bulk band gap. The giant spin-splitting of this band ensures a substantial spin asymmetry of the inelastic mean free path of quasiparticles with different spin orientations.