Signatures of correlated defects in an ultra-clean Wigner crystal in the extreme quantum limit

Abstract

Low-disorder two-dimensional electron systems in the presence of a strong, perpendicular magnetic field terminate at very small Landau level filling factors in a Wigner crystal (WC), where the electrons form an ordered array to minimize the Coulomb repulsion. The nature of this exotic, many-body, quantum phase is yet to be fully understood and experimentally revealed. Here we probe one of WC's most fundamental parameters, namely the energy gap that determines its low-temperature conductivity, in record-mobility, ultra-high-purity, two-dimensional electrons confined to GaAs quantum wells. The WC domains in these samples contain $\simeq$ 1000 electrons. The measured gaps are a factor of three larger than previously reported for lower quality samples, and agree remarkably well with values predicted for the lowest-energy, intrinsic, hyper-corelated bubble defects in a WC made of flux-electron composite fermions, rather than bare electrons. The agreement is particularly noteworthy, given that the calculations are done for disorder-free composite fermion WCs, and there are no adjustable parameters. The results reflect the exceptionally high quality of the samples, and suggest that composite fermion WCs are indeed more stable compared to their electron counterparts.

References in corpus (11)

• Phase Diagram of the Low-Density Two-Dimensional Homogeneous Electron Gas
• Melting of a 2D Quantum Electron Solid in High Magnetic Field
• NMR profiling of quantum electron solids in high magnetic fields
• Observation of Spontaneous Ferromagnetism in a Two-Dimensional Electron System
• Fractional Quantum Hall Effect at Landau Level Filling nu=4/11
• Observation of Incompressibility at $\nu =4/11$ and $\nu =5/13$
• Anisotropic, two-dimensional, disordered Wigner solid
• Understanding limits to mobility in ultra-high-mobility GaAs two-dimensional electron systems: The quest for 100 million cm${}^2$/Vs and beyond
• Moving crystal phases of a quantum Wigner solid in an ultra-high-quality 2D electron system
• Correlated states of 2D electrons near the Landau level filling $\nu =1/7$
• Quantum bubble defects in the lowest Landau level crystal

Cited by in corpus (2)

• Competing Many-Body Phases at Small Fillings in Ultrahigh-Quality GaAs 2D Hole Systems: Role of Landau Level Mixing
• Developing fractional quantum Hall states at $\nu$ = $\frac{1}{7}$ and $\frac{2}{11}$ in the presence of significant Landau level mixing