Three-dimensional bulk band dispersion in polar BiTeI with giant Rashba-type spin splitting

TL;DR

This study uses soft x-ray ARPES to reveal the 3D bulk band structure of BiTeI, demonstrating giant Rashba-type spin splitting in a bulk polar semiconductor, confirmed by first-principles calculations.

Contribution

First experimental demonstration of 3D Rashba spin splitting in bulk BiTeI using SX-ARPES, aligning with theoretical predictions.

Findings

Giant spin splittings of ~300 meV at the band edges

Direct evidence of 3D Rashba spin splitting in a bulk material

Good agreement between experimental data and first-principles calculations

Abstract

In layered polar semiconductor BiTeI, giant Rashba-type spin-split band dispersions show up due to the crystal structure asymmetry and the strong spin-orbit interaction. Here we investigate the 3-dimensional (3D) bulk band structures of BiTeI using the bulk-sensitive $h\nu$-dependent soft x-ray angle resolved photoemission spectroscopy (SX-ARPES). The obtained band structure is shown to be well reproducible by the first-principles calculations, with huge spin splittings of ${\sim}300$ meV at the conduction-band-minimum and valence-band-maximum located in the $k_z=\pi/c$ plane. It provides the first direct experimental evidence of the 3D Rashba-type spin splitting in a bulk compound.