Fermi Contour Anisotropy of GaAs Electron-Flux Composite Fermions in Parallel Magnetic Fields

Abstract

In high-quality two-dimensional electrons confined to GaAs quantum wells, near Landau level filling factors $\nu =$ 1/2 and 1/4, we observe signatures of the commensurability of the electron-flux composite fermion cyclotron orbits with a unidirectional periodic density modulation. Focusing on the data near $\nu =1/2$, we directly and quantitatively probe the shape of the composite fermions' cyclotron orbit, and therefore their Fermi contour, as a function of magnetic field ($B_{||}$) applied parallel to the sample plane. The composite fermion Fermi contour becomes severely distorted with increasing $B_{||}$ and appears to be elliptical, in sharp contrast to the electron Fermi contour which splits as the system becomes bilayer-like at high $B_{||}$. We present a simple, qualitative model to interpret our findings.

5 pages, 4 figures

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• Acoustic Wave Absorption as a Probe of Dynamical Geometrical Response of Fractional Quantum Hall Liquids
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• Anisotropic, two-dimensional, disordered Wigner solid
• Exact results for model wave functions of anisotropic composite fermions in the fractional quantum Hall effect
• Transference of Fermi Contour Anisotropy to Composite Fermions
• Geometric Resonance of Composite Fermions near Bilayer Quantum Hall States
• Unconventional anisotropic even-denominator fractional quantum Hall state in a system with mass anisotropy
• Composite Fermions with a Warped Fermi Contour
• Composite-fermion pairing at half and quarter filled lowest Landau level
• Direct observation of composite fermions and their fully spin-polarized Fermi sea near $\nu =5/2$
• Numerical study of anisotropy in a composite Fermi liquid
• Anisotropy Driven Transition from Moore-Read State to Quantum Hall Stripes
• Geometric Resonance of Four-Flux Composite Fermions
• Observation of An Anisotropic Wigner Crystal
• Connection between Fermi contours of zero-field electrons and $\nu =\frac{1}{2}$ composite fermions in two-dimensional systems
• Tunnel transport and interlayer excitons in bilayer fractional quantum Hall systems
• Valley Stoner Instability of the Composite Fermi Sea
• Anisotropic composite fermions and fractional quantum Hall effect
• Geometry of flux attachment in anisotropic fractional quantum Hall states
• Interaction-dependent anisotropy of fractional quantum Hall states
• Determination of the Fermi Contour and Spin-polarization of $\nu =3/2$ Composite Fermions via Ballistic Commensurability Measurements
• Cyclotron Orbits of Composite Fermions in the Fractional Quantum Hall Regime
• Valley-tunable, even-denominator fractional quantum Hall state in the lowest Landau level of an anisotropic system
• Tuning of Fermi Contour Anisotropy in GaAs (001) 2D Holes via Strain
• Search for Composite Fermions at Filling Factor 5/2: Role of Landau Level and Subband Index
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• $2{\mathbf{k}}_{\mathbf{F}}$ Density Wave Instability of Composite Fermi Liquid
• Nonperturbative emergence of Dirac fermion in strongly correlated composite fermions of fractional quantum Hall effects