TY - JOUR
T1 - De Haas-van Alphen effect and energy gaps of a correlated two-dimensional electron system in an AlAs two-valley pseudospin system
AU - Windisch, T.
AU - Huang, X.
AU - Dasgupta, S.
AU - Rupprecht, B.
AU - Heyn, Ch
AU - Bichler, M.
AU - Fontcubertai Morral, A.
AU - Grayson, M.
AU - Abstreiter, G.
AU - Wilde, M. A.
AU - Grundler, D.
PY - 2009/11/9
Y1 - 2009/11/9
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevB.80.205306
DO - 10.1103/PhysRevB.80.205306
M3 - Article
AN - SCOPUS:77954739337
SN - 1098-0121
VL - 80
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 20
M1 - 205306
ER -