Possible transport evidence for a surface state gap in a magnetically doped topological insulator

ORAL

Abstract

We report magnetoresistance measurements in thin films of a magnetically doped topological insulator Bi$_{2-x}$Mn$_x$Se$_3$ synthesized by molecular beam epitaxy. We observe a crossover from positive magnetoresistance to negative magnetoresistance at low temperature ($T \la 15$ K), accompanied by onset of ferromagnetic signatures (hysteresis and anisotropic magnetoresistance). The observations are consistent with the prediction of a transition of diffusive quantum transport from the symplectic to the unitary class due to a magnetically induced surface state gap. This interpretation is supported by the observation of strongly suppressed surface states at the Dirac point in angle-resolved photoemission spectroscopy. We use the magneto-optical Kerr effect, anomalous Hall effect, SQUID magnetometry, electron microscopy and scanning tunneling microscopy to clarify the source of the ferromagnetism in these samples. Supported by DARPA, ONR and NSF-MRSEC.

–

Authors

  • D.M. Zhang

    • Penn State University, University Park PA 16802
    • Dept. of Physics, Penn State University, University Park 16802
    • Dept. of Physics, Penn State University, University Park PA 16802

  • Anthony Richardella

    • Penn State University, University Park PA 16802
    • Dept. of Physics, Penn State University, University Park 16802
    • Dept. of Physics, Penn State University, University Park PA 16802
    • Penn State University
    • Pennsylvania State University

  • D.W. Rench

    • Dept. of Physics, Penn State University, University Park 16802

  • A. Kandala

    • Dept. of Physics, Penn State University, University Park 16802

  • T.C. Flanagan

    • Dept. of Physics, Penn State University, University Park 16802

  • P. Schiffer

    • Dept. of Physics, Penn State University, University Park 16802

  • N. Samarth

    • Penn State University, University Park PA 16802
    • Dept. of Physics, Penn State University, University Park PA 16802
    • Dept. of Physics, Penn State University, University Park 16802
    • Pennsylvania State University
    • Center for Nanoscale Science and Materials Research Institute, Penn State University, University Park PA 16802

  • Su-Yang Xu

    • Princeton University
    • Dept. of Physics, Princeton University, Princeton, NJ 08544
    • Joseph Henry Laboratory and Dept. of Physics, Princeton University

  • H. Beidenkopf

    • Joseph Henry Laboratory, Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
    • Dept. of Physics, Princeton University, Princeton, NJ 08544

  • Ali Yazdani

    • Joseph Henry Laboratory, Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
    • Princeton University
    • Dept. of Physics, Princeton University, Princeton, NJ 08544

  • M. Zahid Hasan

    • Princeton University
    • Dept. of Physics, Princeton University, Princeton, NJ 08544
    • Princeton University Physics
    • Joseph Henry Laboratory and Dept. of Physics, Princeton University

  • A.L. Yeats

    • Center for Spintronics and Quantum Computation, University of California, Santa Barbara CA 93106
    • Dept. of Physics, University of California, Santa Barbara CA 93016

  • B.B. Buckley

    • Dept. of Physics, University of California, Santa Barbara CA 93016

  • P. Klimov

    • Dept. of Physics, University of California, Santa Barbara CA 93016

  • D.D. Awschalom

    • Dept. of Physics, University of California, Santa Barbara CA 93016
    • University of California Santa Barbara
    • Center for Spintronics and Quantum Computation, University of California, Santa Barbara, CA 93106
    • UCSB
    • Center for Spintronics and Quantum Computation, University of California, Santa Barbara, CA