The surface-state of the topological insulator Bi$_2$Se$_3$ revealed by cyclotron resonance

TL;DR

This study employs high-frequency spectroscopy to isolate and analyze the surface states of the topological insulator Bi$_2$Se$_3$, overcoming bulk conductivity issues and revealing the surface's cyclotron resonance.

Contribution

It introduces a high-frequency spectroscopic method to selectively probe the surface conductivity of Bi$_2$Se$_3$, distinguishing it from bulk effects.

Findings

Observation of a crossover from 3D quantum oscillations to 2D cyclotron resonance.

Identification of surface state properties via high-frequency spectroscopy.

Demonstration of surface state dominance at GHz frequencies.

Abstract

To date transport measurements of topological insulators have been dominated by the conductivity of the bulk, leading to substantial difficulties in resolving the properties of the surface. To this end, we use high magnetic field, rf- and microwave-spectroscopy to selectively couple to the surface conductivity of Bi$_2$Se$_3$ at high frequency. In the frequency range of a few GHz we observe a crossover from quantum oscillations indicative of a small 3D Fermi surface, to cyclotron resonance indicative of a 2D surface state.