Evidence for Two Different Solid Phases of Two Dimensional Electrons in High Magnetic Fields

TL;DR

This study provides evidence for two distinct solid phases of two-dimensional electrons in high magnetic fields, identified through RF spectroscopy, with differences in their resonance behaviors and correlation lengths.

Contribution

The paper reveals the existence of two different pinned solid phases of 2D electrons, characterized by distinct resonances and correlation properties, expanding understanding of electron solid states in high magnetic fields.

Findings

Two different resonances identified as separate solid phases.

WS-A shows large correlation length and dispersion.

WS-B lacks dispersion and has different resonance characteristics.

Abstract

We have performed RF spectroscopy on very high quality two dimensional electron systems in the high magnetic field insulating phase, usually associated with a Wigner solid (WS) pinned by disorder. We have found two different resonances in the frequency dependent real diagonal conductivity spectrum and we interpret them as coming from \textit{two} different pinned solid phases (labeled as "WS-A" and "WS-B"). The resonance of WS-A is observable for Landau level filling $\nu$$<$2/9 (but absent around the $\nu$=1/5 fractional quantum Hall effect (FQHE)); it then \textit{crosses over} for $\nu$$<$0.18 to the different WS-B resonance which dominates the spectrum at $\nu$$<$0.125. Moreover, WS-A resonance is found to show dispersion with respect to the size of transmission line, indicating that WS-A has a large correlation length (exceeding $\sim$100 $\mu$m); in contrast no such behavior is found for WS-B. We suggest that quantum correlations such as those responsible for FQHE may play an important role in giving rise to such different solids.