Microwave spectroscopic observation of a Wigner solid within the 1/2 fractional quantum Hall effect

TL;DR

This paper presents microwave spectroscopy evidence for a Wigner solid formed by dipolar quasiholes in a wide quantum well near the half-integer fractional quantum Hall state, revealing new insights into correlated electron states.

Contribution

It provides the first direct spectroscopic evidence of a Wigner solid of dipolar quasiholes at $ u \, ext{close to} \, 1/2$ in a wide quantum well, advancing understanding of fractional quantum Hall states.

Findings

Detected microwave resonance indicative of Wigner solid formation

Identified dipolar quasiholes as the solid's constituents

Linked the observed spectra to the $ u=1/2$ fractional quantum Hall regime

Abstract

The fractional quantum Hall effect (FQHE) states at half integer Landau fillings ($\nu$) have long been of great interest, since they have correlations that differ from those of the fundamental Laughlin states found at odd denominators. At $\nu=1/2$ the FQHE has been observed in wide or double quantum wells, and is ascribed to the two-component Halperin-Laughlin $\Psi_{331}$ state. $\Psi_{331}$ excitations carry charge $\pm e/4$, like the carriers of $\nu=5/2$ states which are of interest in quantum computation. Further, such an excitation (quasiparticle or -hole) of $\Psi_{331}$ has unequal, opposite charge in the top and bottom layers, and hence an up or down dipole moment. Here we report evidence for a Wigner solid (WS) of such dipolar quasiholes from a quantitative study of the microwave spectra of a wide quantum well (WQW) at $\nu$ close to 1/2.