Even-denominator Fractional Quantum Hall Effect at a Landau Level Crossing

ORAL

Abstract

The fractional quantum Hall (FQH) effect, observed in two-dimensional charged particles at high magnetic fields, occurs when the filling factor $\nu$ of the quantized Landau levels is a fraction which, with very few exceptions, has an odd denominator. Here we describe unexpected phenomena in two-dimensional hole systems confined to GaAs quantum wells. We observe an unusual crossing of the two lowest-energy Landal levels. The crossing leads to a weakening or disappearance of the commonly seen odd-denominator FQH states in the filling range $1/3 < \nu < 2/3$. But, surprisingly, a new FQH state at the even-denominator filling $\nu= 1/2$ comes to exist at the crossing.

*We acknowledge support through the DOE BES (DE-FG02-00-ER45841) for measurements, and the Gordon and Betty Moore Foundation (Grant GBMF2719), Keck Foundation, and the NSF (DMR-0904117, DMR-1305691 and MRSEC DMR-0819860) for sample fabrication.

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Authors

  • Yang Liu

    • Princeton Univ

  • Sukret Hasdemir

    • Princeton Univ
    • Princeton University

  • Dobromir Kamburov

    • Princeton Univ

  • Aurelius Graninger

    • Princeton Univ

  • Mansour Shayegan

    • Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
    • Princeton Univ

  • L.N. Pfeiffer

    • Princeton University
    • Princeton Univ
    • Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
    • Department of Electrical Engineering, Princeton University

  • K.W. West

    • Princeton University
    • Princeton Univ
    • Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA

  • Kirk Baldwin

    • Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA
    • Princeton Univ
    • Princeton University

  • Roland Winkler

    • Northern Illinois University
    • Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA
    • Princeton Univ