Pressure tuning the Fermi level through the Dirac point of giant Rashba semiconductor BiTeI

Area of Science:

• Condensed Matter Physics
• Materials Science
• Semiconductor Physics

Background:

• BiTeI is a giant Rashba semiconductor with a unique band structure.
• Strong spin-orbit coupling in BiTeI leads to a split conduction band bottom, forming a 'Dirac point'.
• Understanding pressure effects is crucial for exploring novel quantum phenomena in such materials.

Purpose of the Study:

• To investigate the electronic properties of BiTeI under applied pressure.
• To identify changes in Fermi surface topology with increasing pressure.
• To explore the proximity to a topological quantum phase transition.

Main Methods:

• Shubnikov-de Haas oscillations measurements were performed on BiTeI.
• Applied pressures ranged up to approximately 2 GPa.
• A simple model was developed to analyze pressure-dependent parameters.

Main Results:

• A high-frequency Shubnikov-de Haas oscillation was observed at all pressures.
• A second, low-frequency oscillation emerged between 0.3-0.7 GPa, indicating a second Fermi surface.
• The chemical potential was found to shift upwards, crossing the Dirac point under pressure.

Conclusions:

• The emergence of a second Fermi surface is attributed to the chemical potential crossing the Dirac point.
• The developed model quantitatively agrees with first-principles calculations and experiments.
• Pressure is shown to drive BiTeI closer to a predicted topological quantum phase transition.