Thermal Activation Signatures of the Anderson Insulator and the Wigner Solid forming near $\nu=1$

TL;DR

This paper investigates the activation energy behavior in the integer quantum Hall regime near $ u=1$, revealing a non-monotonic dependence linked to phase transitions between Anderson insulator and Wigner solid phases.

Contribution

It provides the first detailed experimental analysis of activation energy signatures across the transition from Anderson insulator to Wigner solid near $ u=1$ in quantum Hall systems.

Findings

Activation energy shows a dramatic non-monotonic dependence on magnetic field.

A surprising minimum in activation energy occurs at the phase boundary.

Results constrain theories of the quantum Hall Wigner solid.

Abstract

When interactions overcome disorder, integer quantum Hall plateaus support topological phases with different bulk insulators. In the center of the $\nu=1$ plateau the bulk is an Anderson-type insulator, while in the flanks of the plateau the bulk is the integer quantum Hall Wigner solid. We find that the activation energy along the $\nu=1$ plateau exhibits a very dramatic non-monotonic dependence on the magnetic field, a dependence that is strongly correlated with the stability regions of the two phases. Furthermore, the activation energy has an unexpected minimum at the boundary between the Anderson insulator and the Wigner solid. Our findings constrain the theory of the integer quantum Hall Wigner solid, determine its thermodynamic properties, and reveal novel behavior at the boundary between the Anderson insulator and the Wigner solid.