Dirac cone shift of a passivated topological Bi2Se3 interface state

TL;DR

This study uses terahertz spectroscopy to analyze a passivated Bi2Se3 topological interface, revealing a Dirac cone shift, reduced potential fluctuations, and high mobility near the Dirac point.

Contribution

First spectroscopic characterization of a single topological interface state from Dirac point to above conduction band edge in passivated Bi2Se3.

Findings

Dirac point shifts towards mid-gap with Fermi energy.

Potential fluctuations are around 50 meV near the Dirac point.

High mobility of 3500 cm2/Vs achieved near the Dirac point.

Abstract

Gated terahertz cyclotron resonance measurements on epitaxial Bi2Se3 thin films capped with In2Se3 enable the first spectroscopic characterization of a single topological interface state from the vicinity of the Dirac point to above the conduction band edge. A precipitous drop in the scattering rate with Fermi energy is observed that is interpreted as the surface state decoupling from bulk states and evidence of a shift of the Dirac point towards mid-gap. Near the Dirac point, potential fluctuations of 50 meV are deduced from an observed loss of differential optical spectral weight near the Dirac point. Potential fluctuations are reduced by a factor of two at higher surface Fermi levels in the vicinity of the conduction band edge inferred from the width of the scattering rate step. The passivated topological interface state attains a high mobility of 3500 cm2/Vsec near the Dirac point.