Temperature dependent infrared spectroscopy of the Rashba spin-splitting semiconductor BiTeI

TL;DR

This study uses temperature-dependent infrared spectroscopy to explore the electronic and vibrational properties of BiTeI, revealing new surface-related optical features and complex phonon behavior linked to Rashba spin-splitting.

Contribution

It reports novel low-energy intraband transitions and multiple vibrational modes, suggesting surface effects influence the optical response of BiTeI beyond bulk band structure considerations.

Findings

Observation of a 40 meV intraband transition

Detection of numerous asymmetric vibrational modes

Surface topology impacts optical properties

Abstract

We performed temperature dependent infrared spectroscopy measurements on BiTeI single crystals, which exhibit large Rashba spin-splitting. Similar to a previous optical study, we found electronic excitations in good agreement with spin-split electronic bands. In addition, we report a low energy intraband transition with an onset energy of about 40 meV and an unexpectedly large number of vibrational modes in the far-infrared spectral region. At least some of the modes have asymmetric Fano line-shape. These new observations cannot be explained considering only the bulk band structure or crystal symmetry of BiTeI, and we proposed that the optical response is also affected by the surface topology.