Giant ambipolar Rashba effect in a semiconductor: BiTeI

TL;DR

This paper reports the discovery of a giant, robust spin-orbit splitting in the semiconductor BiTeI, which can be tuned to achieve ambipolar conduction, making it promising for spintronic applications.

Contribution

It demonstrates the presence of a large, stable Rashba spin splitting and tunable ambipolar conduction in BiTeI, a non-centrosymmetric semiconductor.

Findings

Giant spin-orbit splitting observed in bulk and surface states

Fermi level tunability via surface termination

Spin splitting remains stable despite surface potential changes

Abstract

We observe a giant spin-orbit splitting in bulk and surface states of the non-centrosymmetric semiconductor BiTeI. We show that the Fermi level can be placed in the valence or in the conduction band by controlling the surface termination. In both cases it intersects spin-polarized bands, in the corresponding surface depletion and accumulation layers. The momentum splitting of these bands is not affected by adsorbate-induced changes in the surface potential. These findings demonstrate that two properties crucial for enabling semiconductor-based spin electronics -- a large, robust spin splitting and ambipolar conduction -- are present in this material.