Probing electron-electron interaction in quantum Hall systems with scanning tunneling spectroscopy

TL;DR

This study uses low-temperature scanning tunneling spectroscopy to investigate electron-electron interactions in a quantum Hall system, revealing exchange effects and Coulomb gaps at very small length scales.

Contribution

It demonstrates the capability to probe electron-electron interactions at nanometer scales in quantum Hall systems using advanced spectroscopy.

Findings

Observation of exchange-enhanced spin splitting

Detection of Coulomb gap at the Fermi level

Validation of theoretical calculations with experimental data

Abstract

Using low-temperature scanning tunneling spectroscopy applied to the Cs-induced two-dimensional electron system (2DES) on p-type InSb(110), we probe electron-electron interaction effects in the quantum Hall regime. The 2DES is decoupled from p-doped bulk states and exhibits spreading resistance within the insulating quantum Hall phases. In quantitative agreement with calculations we find an exchange enhancement of the spin splitting. Moreover, we observe that both the spatially averaged as well as the local density of states feature a characteristic Coulomb gap at the Fermi level. These results show that electron-electron interaction effects can be probed down to a resolution below all relevant length scales.