Abstract

Understanding and control of spin degrees of freedom on the surfaces of topological materials are key to future applications as well as for realizing novel physics such as the axion electrodynamics associated with time-reversal (TR) symmetry breaking on the surface. We experimentally demonstrate magnetically induced spin reorientation phenomena simultaneous with a Dirac-metal to gapped-insulator transition on the surfaces of manganese-doped Bi2Se3 thin films. The resulting electronic groundstate exhibits unique hedgehog-like spin textures at low energies, which directly demonstrate the mechanics of TR symmetry breaking on the surface. We further show that an insulating gap induced by quantum tunnelling between surfaces exhibits spin texture modulation at low energies but respects TR invariance. These spin phenomena and the control of their Fermi surface geometrical phase first demonstrated in our experiments pave the way for the future realization of many predicted exotic magnetic phenomena of topological origin.

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Acknowledgements

Work at Princeton University is supported by the US National Science Foundation Grant, NSF-DMR-1006492. M.Z.H. acknowledges visiting-scientist support from Lawrence Berkeley National Laboratory and additional partial support from the A. P. Sloan Foundation and NSF-DMR-0819860. The spin-resolved and spin-integrated photoemission measurements using synchrotron X-ray facilities are supported by the Swedish Research Council, the Knut and Alice Wallenberg Foundation, the Swiss Light Source, the Swiss National Science Foundation, the German Federal Ministry of Education and Research, and the Basic Energy Sciences of the US Department of Energy. Theoretical computations are supported by the US Department of Energy (DE-FG02-07ER46352 and AC03-76SF00098) as well as the National Science Council and Academia Sinica in Taiwan, and benefited from the allocation of supercomputer time at NERSC and Northeastern University’s Advanced Scientific Computation Center. Sample growth and characterization are supported by US DARPA (N66001-11-1-4110). We gratefully acknowledge A. Preobrajenski for beamline assistance on XMCD measurements (supported by DE-FG02-05ER46200) at the D1011 beamline at Maxlab in Lund, Sweden. We acknowledge helpful discussions with S-Q. Shen and L. Balents. We also thank S-K. Mo and A. Fedorov for beamline assistance on spin-integrated photoemission measurements (supported by DE-FG02-05ER46200) at Lawrence Berkeley National Laboratory (The synchrotron facility is supported by the US DOE).

Author information

Affiliations

  1. Joseph Henry Laboratory, Department of Physics, Princeton University, Princeton, New Jersey 08544, USA

    • Su-Yang Xu
    • , Madhab Neupane
    • , Chang Liu
    • , L. Andrew Wray
    • , Nasser Alidoust
    •  & M. Zahid Hasan
  2. Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802-6300, USA

    • Duming Zhang
    • , Anthony Richardella
    •  & Nitin Samarth
  3. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94305, USA

    • L. Andrew Wray
  4. MAX-lab, PO Box 118, S-22100 Lund, Sweden

    • Mats Leandersson
    •  & Thiagarajan Balasubramanian
  5. Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Str. 15, D-12489 Berlin, Germany

    • Jaime Sánchez-Barriga
    •  & Oliver Rader
  6. Swiss Light Source, Paul Scherrer Institute, CH-5232, Villigen, Switzerland

    • Gabriel Landolt
    • , Bartosz Slomski
    •  & Jan Hugo Dil
  7. Physik-Institute, Universitat Zurich-Irchel, CH-8057 Zurich, Switzerland

    • Gabriel Landolt
    • , Bartosz Slomski
    • , Jan Hugo Dil
    •  & Jürg Osterwalder
  8. Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan

    • Tay-Rong Chang
    •  & Horng-Tay Jeng
  9. Institute of Physics, Academia Sinica, Taipei 11529, Taiwan

    • Horng-Tay Jeng
  10. Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA

    • Hsin Lin
    •  & Arun Bansil
  11. Princeton Center for Complex Materials, Princeton Institute for Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, USA

    • M. Zahid Hasan

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Contributions

S-Y.X. performed the experiments with assistance from M.N., C.L., L.A.W., N.A. and M.Z.H.; D.Z., A.R. and N.S. provided samples; M.L., T.B., J.S-B., O.R., G.L., B.S., J.H.D. and J.O. provided beamline assistance; T-R.C., H-T.J., H.L. and A.B. carried out the theoretical calculations; M.Z.H. was responsible for the overall direction, planning and integration among the different research units.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to M. Zahid Hasan.

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https://doi.org/10.1038/nphys2351

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