Shubnikov-de Haas oscillations from topological surface states of metallic Bi$_2$Se$_{2.1}$Te$_{0.9}$

TL;DR

This study observes Shubnikov-de Haas oscillations in metallic Bi$_2$Se$_{2.1}$Te$_{0.9}$, revealing surface states with Dirac dispersion and characterizing their conduction properties through quantum oscillation analysis.

Contribution

It demonstrates the detection of topological surface state oscillations in a metallic topological insulator using quantum oscillation measurements and Lifshitz-Kosevich analysis.

Findings

Surface oscillations originate from Dirac surface states.

Quantum oscillations are detectable at lower magnetic fields due to bulk band structure.

Surface conduction parameters are quantitatively characterized.

Abstract

We have studied the quantum oscillations in the conductivity of metallic, p-type Bi$_2$Se$_{2.1}$Te$_{0.9}$. The dependence of the oscillations on the angle of the magnetic field with the surface as well as the Berry phase determined from the Landau level fan plot indicate that the observed oscillations arise from surface carriers with the characteristic Dirac dispersion. Several quantities characterizing the surface conduction are calculated employing the Lifshitz-Kosevich theory. The low value of the Fermi energy with respect to the Dirac point is consistent with the metallic character of the bulk hole carriers. We conclude that, due to the peculiar shape of the valence band, the Shubnikov-de Haas oscillations of the bulk carriers are shifted to higher magnetic fields which allows for the detection of the quantum oscillations from the topological surface states at lower field.