De-Pinning Transition of Bubble Phases in a High Landau Level

TL;DR

This paper investigates the de-pinning transition of bubble phases in high Landau levels through nonlinear transport measurements, revealing a phase diagram and discussing a topological phase transition related to reentrant integer quantum Hall states.

Contribution

It provides the first direct conductivity measurements of bubble phase de-pinning using Corbino geometry, complementing microwave studies and mapping the phase diagram.

Findings

Identification of the threshold electric field for de-pinning

Mapping of the phase diagram of reentrant states

Discussion of a topological phase transition

Abstract

While in the lowest Landau level the electron-electron interaction leads to the formation of the Wigner crystal, in higher Landau levels a solid phase with multiple electrons in a lattice site of crystal was predicted, which was called the bubble phase. Reentrant integer quantum Hall states are believed to be the insulating bubble phase pinned by disorder. We carry out nonlinear transport measurements on the reentrant states and study the de-pinning of the bubble phase, which is complementary to previous microwave measurements and provides unique information. In this study, conductivity is directly measured with Corbino geometry. Based on the threshold electric field of de-pinning, a phase diagram of the reentrant state is mapped. We discuss an interaction-driven topological phase transition between the integer quantum Hall state and the reentrant integer quantum Hall state.