Fractional quantum Hall effects in In0.75Ga0.25As bilayer electron systems observed as \u201cFinger print\u201d

Kanji Takehana,Siro Hidaka,Akira Fujimoto,Syoji Yamada,Masashi Akabori,Yasutaka Imanaka

doi:10.1038/s41598-019-43290-8

Abstract

Observations of fractional quantum Hall (FQH) plateaus are reported in bilayer electron gas system in wide (>80 nm) In0.75Ga0.25As wells. Several q/p (p = 5, 3, and 2, q > 5) QH states are confirmed at high temperatures (~1.6 K) when the critical conditions including an electron density imbalance as well as a dynamical resistance behavior at the bilayer-monolayer transition are properly satisfied. The former leads to a quantum limit in either of the layers and the latter might bring a meta-stable nature into FQH phenomena. Such a behavior occurs as a probability process associating with impurities or defects in the wells, they inevitably reflect the local structural landscapes of each sample. This is verified by the new finding that the kinds of fractional plateaus (what set of fractional filling factors) appeared are different depending on the samples, that is, they are the “finger print” in each sample.

Highlights

Integer[1,2,3] and fractional[4,5] quantum Hall effects (IQHEs and FQHEs) are remarkable phenomena arising from the distinctive dynamics of two-dimensional electron gas (2DEG) under strong perpendicular magnetic fields
For example, interlayer Coulomb interactions in a multilayer structure have been predicted to lead even denominator fractional quantum Hall (FQH) states. This prediction has been followed by the successive observations of new FQH states at ν = 1/2 for 2DEG systems in a WSQW12,13 or a DQW14
Second example nearly concerned with this article is the report[15,16] on the stability discussion of the q/3 states in GaAs wide-single quantum well (WSQW) systems: The demonstrated Rxx data show that the q/3 states are confirmed to be stable even at filing factors up to ν = 17/3, when EF lies in a ground state (N = 0) LLs regardless of whether the ground LL belongs to the upper or lower 2DEG subband

Summary

Introduction

Integer[1,2,3] and fractional[4,5] quantum Hall effects (IQHEs and FQHEs) are remarkable phenomena arising from the distinctive dynamics of two-dimensional electron gas (2DEG) under strong perpendicular magnetic fields. In FQHE, the gaps in the excitation spectrum, which are a direct result of the intra-layer Coulomb interaction, play an important role This effect is a so-called incompressible phase of quantum liquid state described by Laughlin wave function[6]. For example, interlayer Coulomb interactions in a multilayer structure have been predicted to lead even denominator FQH states This prediction has been followed by the successive observations of new FQH states at ν = 1/2 for 2DEG systems in a WSQW12,13 or a DQW14. This often appears not as an electron density inhomogeneity but as an in-plane mobility anisotropy in InxGa1−xAs hetero-junctions Due to these reasons, the disorder in the In0.5Ga0.5As 2DEGs still remains at relatively higher level even at low temperatures. The imbalanced electron density distribution crucial for giving the quantum limit condition at one interface as well as the metastable nature frequently seen at bilayer-monolayer transition are considered to facilitate the observation

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Conclusion