Origin of giant bulk Rashba splitting: Application to BiTeI

TL;DR

This paper identifies the key conditions for giant bulk Rashba splitting, demonstrating that BiTeI fulfills these through first-principles calculations and revised crystal structure predictions.

Contribution

It establishes the necessary conditions for giant Rashba splitting in bulk systems and applies them to accurately predict the structure and electronic properties of BiTeI.

Findings

BiTeI exhibits giant Rashba splitting.

Correct crystal structure of BiTeI is identified.

Negative crystal field splitting enables the third condition.

Abstract

We theoretically propose the necessary conditions for realization of giant Rashba splitting in bulk systems. In addition to (i) the large atomic spin-orbit interaction in an inversion-asymmetric system, the following two conditions are further required; (ii) a narrow band gap, and (iii) the presence of top valence and bottom conduction bands of symmetrically the same character. As a representative example, using the first principles calculations, the recently discovered giant bulk Rashba splitting system BiTeI is shown to fully fulfill all these three conditions. Of particular importance, by predicting the correct crystal structure of BiTeI, different from what has been believed thus far, the third criterion is demonstrated to be met by a negative crystal field splitting of the top valence bands.