Abstract
It was recently shown that BiTeI, a semiconductor with polar crystal structure, possesses a giant spin splitting of electrons, which has been interpreted in terms of Rashba-type spin-orbit coupling. Here we use high field magneto-optical spectroscopy to quantify the deviations of the conduction-band profile from this appealing, but at the same time, strongly simplifying model.
We find that the optical response-comprising a series of inter-Landau level excitations-can be described by the Rashba model only at low magnetic fields. In contrast, the high-field response appears to be more consistent with a simple picture of massless electrons in a conical band.
This points towards more linear rather than parabolic dispersion at energies well above the bottom of the conduction band.