Quantum Oscillations in a Topological Insulator Bi$_2$Te$_2$Se with Large Bulk Resistivity (6 $\Omega$cm)

TL;DR

This paper reports the observation of quantum oscillations in a topological insulator with high bulk resistivity, revealing surface Dirac states and evidence of fractional-filling states, advancing understanding of topological surface conduction.

Contribution

It provides experimental evidence of quantum oscillations and fractional states in Bi$_2$Te$_2$Se with high bulk resistivity, highlighting surface state properties.

Findings

Observation of Shubnikov-de Haas oscillations in Bi$_2$Te$_2$Se

Identification of Dirac surface states with a half-integer shift

Evidence of fractional-filling states at high magnetic fields

Abstract

We report the observation of prominent Shubnikov-de Haas oscillations in a Topological Insulator, Bi$_2$Te$_2$Se, with large bulk resistivity (6 $\Omega$cm at 4 K). By fitting the SdH oscillations, we infer a large metallicity parameter $k_F\ell$ = 41, with a surface mobility ($\mu_s\sim$ 2,800 cm$^2$/Vs) much larger than the bulk mobility ($\mu_b\sim$ 50 cm$^2$/Vs). The plot of the index fields $B_{\nu}$ vs. filling factor $\nu$ shows a $\frac12$-shift, consistent with massless, Dirac states. Evidence for fractional-filling states is seen in an 11-T field.