Effect of Oscillating Landau Bandwidth on the Integer Quantum Hall Effect in a Unidirectional Lateral Superlattice

TL;DR

This study investigates how a unidirectional periodic potential modulation affects the activation gaps of odd-integer quantum Hall states in a 2DEG, revealing a bandwidth-dependent reduction that vanishes at flat band conditions.

Contribution

It provides experimental evidence linking Landau bandwidth oscillations to the suppression of quantum Hall activation gaps in a modulated 2DEG.

Findings

Activation gaps are reduced in the ULSL compared to unmodulated regions.

The gap reduction correlates with Landau bandwidth variations due to commensurability.

The decrement disappears at flat band conditions.

Abstract

We have measured activation gaps for odd-integer quantum Hall states in a unidirectional lateral superlattice (ULSL) -- a two-dimensional electron gas (2DEG) subjected to a unidirectional periodic modulation of the electrostatic potential. By comparing the activation gaps with those simultaneously measured in the adjacent section of the same 2DEG sample without modulation, we find that the gaps are reduced in the ULSL by an amount corresponding to the width acquired by the Landau levels through the introduction of the modulation. The decrement of the activation gap varies with the magnetic field following the variation of the Landau bandwidth due to the commensurability effect. Notably, the decrement vanishes at the flat band conditions.