Correlated states of 2D electrons near the Landau level filling $\nu =1/7$

Abstract

The ground state of two-dimensional electron systems (2DESs) at low Landau level filling factors ($\nu \lesssim 1/6$) has long been a topic of interest and controversy in condensed matter. Following the recent breakthrough in the quality of ultra-high-mobility GaAs 2DESs, we revisit this problem experimentally and investigate the impact of reduced disorder. In a GaAs 2DES sample with density $n=6.1\times 10^{10}$ /cm${}^2$ and mobility $\mu =25\times 10^6$ cm${}^2$/Vs, we find a deep minimum in the longitudinal magnetoresistance ($R_{xx}$) at $\nu =1/7$ when $T\simeq 104$ mK. There is also a clear sign of a developing minimum in the $R_{xx}$ at $\nu =2/13$. While insulating phases are still predominant when $\nu \lesssim 1/6$, these minima strongly suggest the existence of fractional quantum Hall states at filling factors that comply with the Jain sequence $\nu =p/(2mp\pm 1)$ even in the very low Landau level filling limit. The magnetic field dependent activation energies deduced from the relation $R_{xx}\propto e^{E_A/2kT}$ corroborate this view, and imply the presence of pinned Wigner solid states when $\nu \ne p/(2mp\pm 1)$. Similar results are seen in another sample with a lower density, further generalizing our observations.

6 pages, 4 figures

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• Interplay between fractional quantum Hall liquid and crystal phases at low filling
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• Dynamic Response of Wigner Crystals
• Signatures of correlated defects in an ultra-clean Wigner crystal in the extreme quantum limit
• Developing fractional quantum Hall states at even-denominator fillings 1/6 and 1/8
• Unlocking new regimes in fractional quantum Hall effect with quaternions
• Impurity-induced thermal crossover in fractional Chern insulators
• Competing Many-Body Phases at Small Fillings in Ultrahigh-Quality GaAs 2D Hole Systems: Role of Landau Level Mixing
• Evidence for Topological Protection Derived from Six-Flux Composite Fermions
• Developing fractional quantum Hall states at $\nu$ = $\frac{1}{7}$ and $\frac{2}{11}$ in the presence of significant Landau level mixing
• Cascade of fractional quantum Hall states in 2D system
• Interlayer-correlated fractional quantum Hall state in a trilayer electron system
• Disorder-induced strong-field strong-localization in 2D systems