Signatures of Fractional Quantum Hall States in Topological Insulators

TL;DR

This paper reports the experimental observation of fractional quantum Hall states in topological insulators, specifically Bi2Te3, using thermopower measurements to detect strongly correlated surface states in high magnetic fields.

Contribution

It demonstrates the detection of FQH states in topological insulators through thermopower, revealing strongly correlated Dirac surface states and enabling new studies of fractional quantum Hall physics.

Findings

FQH states observed in Bi2Te3 surface states

Thermopower measurements reveal fractional Landau levels

Surface thermopower is significantly higher than bulk

Abstract

The fractional quantum Hall (FQH) state is a topological state of matter resulting from the many-body effect of interacting electrons and is of vast interest in fundamental physics. The experimental observation of topological surface states (SSs) in three-dimensional bulk solids has allowed the study of a correlated chiral Dirac fermion system, which can host a single Dirac valley without spin degeneracy. Recent theoretical studies suggest that the fractional quantum Hall effect (FQHE) might be observable in topological insulators. However, due to the dominant bulk conduction it is difficult to probe the strong correlation effect in topological insulators from resistivity measurements. Here we report the discovery of FQH states in Bi2Te3 from thermopower measurements. The surface thermopower is ten times greater than that of bulk, which makes possible the observation of fractional-filled Landau levels in SSs. Thermopower hence provides a powerful tool to investigate correlated Dirac fermions in topological insulators. Our observations demonstrate that Dirac topological SSs exhibit strongly correlated phases in a high magnetic field, and would enable studies of a variety of exotic fractional quantum Hall physics and other correlated phenomena in this newly discovered chiral Dirac system.