Ultraclean two-dimensional hole systems with mobilities exceeding 10${}^7$ cm${}^2$/Vs

Abstract

Owing to their large effective mass, strong and tunable spin-orbit coupling, and complex band-structure, two-dimensional hole systems (2DHSs) in GaAs quantum wells provide rich platforms to probe exotic many-body physics, while also offering potential applications in ballistic and spintronics devices, and fault-tolerant topological quantum computing. We present here a systematic study of molecular-beam-epitaxy grown, modulation-doped, GaAs (001) 2DHSs where we explore the limits of low-temperature 2DHS mobility by optimizing two parameters, the GaAs quantum well width and the alloy fraction ($x$) of the flanking Al${}_x$Ga${}_{1-x}$As barriers. We obtain a breakthrough in 2DHS mobility, with a peak value $\simeq 18\times 10^6$ cm${}^2$/Vs at a density of 3.8 $\times$ 10${}^{10}$ /cm${}^2$, implying a mean-free-path of $\simeq 57\mu$m. Using transport calculations tailored to our structures, we analyze the operating scattering mechanisms to explain the non-monotonic evolution of mobility with density. We find it imperative to include the dependence of effective mass on 2DHS density, well width, and $x$. We observe concomitant improvement in quality as evinced by the appearance of delicate fractional quantum Hall states at very low density.

arXiv comment10 pages, 4 figures, Accepted in Physical Review Materials

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Cited by in corpus (3)

• 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
• Even-denominator fractional quantum Hall states with spontaneously broken rotational symmetry