Tuning the Fermi level through the Dirac point of giant Rashba semiconductor BiTeI with pressure

TL;DR

This study investigates how applying pressure to the giant Rashba semiconductor BiTeI tunes the Fermi level across the Dirac point, revealing changes in Fermi surfaces and supporting proximity to a topological phase transition.

Contribution

It provides experimental evidence of pressure-induced Fermi level tuning across the Dirac point in BiTeI and introduces a simple model aligning with first-principles calculations.

Findings

Emergence of a second small Fermi surface under pressure

Fermi level crosses the Dirac point with increasing pressure

Parameters support proximity to topological quantum phase transition

Abstract

We report measurements of Shubnikov-de Haas oscillations in the giant Rashba semiconductor BiTeI under applied pressures up to $\sim 2\,\mathrm{GPa}$. We observe one high frequency oscillation at all pressures and one low frequency oscillation that emerges between $\sim 0.3-0.7\,\mathrm{GPa}$ indicating the appearance of a second small Fermi surface. BiTeI has a conduction band bottom that is split into two sub-bands due to the strong Rashba coupling, resulting in a `Dirac point'. Our results suggest that the chemical potential starts below the Dirac point in the conduction band at ambient pressure and moves upward, crossing it as pressure is increased. The presence of the chemical potential above this Dirac point results in two Fermi surfaces. We present a simple model that captures this effect and can be used to understand the pressure dependence of our sample parameters. These extracted parameters are in quantitative agreement with first-principles calculations and other experiments. The parameters extracted via our model support the notion that pressure brings the system closer to the predicted topological quantum phase transition.