De Haas-van Alphen effect and energy gaps of a correlated two-dimensional electron system in an AlAs two-valley pseudospin system

T. Windisch*, X. Huang, S. Dasgupta, B. Rupprecht, Ch Heyn, M. Bichler, A. Fontcubertai Morral, M. Grayson, G. Abstreiter, M. A. Wilde, D. Grundler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

We report highly sensitive de Haas-van Alphen (dHvA) effect measurements on a high-mobility two-dimensional electron system in an AlAs quantum well. Here two valleys are occupied forming a pseudospin system. At 400 mK, the dHvA effect shows pronounced oscillations at filling factors ν=1 to four. In the quantum limit at ν=1 the data are consistent with an interaction-enhanced valley splitting, which exceeds the Zeeman spin splitting in a perpendicular field B. When tilting B the energy gap ΔE at ν=1 shows first an unexpectedly strong angular dependence and then remains constant. This suggests a crossover in the energy gap, most likely from a spin to a pseudospin gap. We attribute the strong initial dependence of ΔE on the tilt angle to skyrmion-type spin excitations. Surprisingly, the dHvA oscillation amplitudes do not display coincidence phenomena at higher filling factors. This is explained by the large valley splitting and avoided crossings of energy levels.

Original languageEnglish (US)
Article number205306
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume80
Issue number20
DOIs
StatePublished - Nov 9 2009

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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