Signatures of an annular Fermi sea

Abstract

We report Shubnikov-de Haas oscillations measurements revealing experimental signatures of an annular Fermi sea that develops near the energy band edge of the excited subband of two-dimensional holes confined in a wide GaAs quantum well. As we increase the hole density, when the Fermi level reaches the excited subband edge, the low-field magnetoresistance traces show a sudden emergence of new oscillations at an unexpectedly large frequency whose value does $\text{not}$ correspond to the (negligible) density of holes in the excited subband. There is also a sharp and significant increase in zero-field resistance near this onset of subband occupation. Guided by numerical energy dispersion calculations, we associate these observations with the unusual shape of the excited subband dispersion which results in a "ring of extrema" at finite wavevectors and an annular Fermi sea. Such a dispersion and Fermi sea have long been expected from energy band calculations in systems with strong spin-orbit interaction but their experimental signatures have been elusive.

arXiv comment5 pages, 4 figures

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• Record-quality GaAs two-dimensional hole systems
• Connection between Fermi contours of zero-field electrons and $\nu =\frac{1}{2}$ composite fermions in two-dimensional systems
• Gate-tunable Electronic Transport in p-type GaSb Quantum Wells
• Tuning of Fermi Contour Anisotropy in GaAs (001) 2D Holes via Strain
• Unconventional transport in low-density two-dimensional Rashba systems
• The linear Dirac spectrum and the Weyl states in the Drude-Sommerfeld topological model
• Fermi surfaces of composite fermions
• Fermi surface instabilities of symmetry-breaking and topological types on the surface of a three-dimensional topological insulator
• Superfluid-insulator transition and the BEC-BCS crossover in the Rashba moat band