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Abstract

Transition-metal dichalcogenides such as WSe2 and MoS2 have electronic band structures that are ideal for hosting many exotic spin–orbit phenomena. Here we investigate the possibility to generate and modulate a giant Zeeman-type spin polarization in WSe2 under an external electric field. By tuning the perpendicular electric field applied to the WSe2 channel with an electric-double-layer transistor, we observe a systematic crossover from weak localization to weak anti-localization in magnetotransport. Our optical reflection measurements also reveal an electrically tunable exciton splitting. Using first-principles calculations, we propose that these are probably due to the emergence of a merely out-of-plane and momentum-independent spin splitting at and in the vicinity of the vertices of the WSe2 Brillouin zone under electric field. The non-magnetic approach for creating such an intriguing spin splitting keeps the system time-reversally invariant, thereby suggesting a new method for manipulating the spin degrees of freedom of electrons.

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  • 19 August 2013

    In the version of this Article originally published online, the equation in the first paragraph should have been: Ĥso = -μBσ · (p × E/2mc2). Also, throughout the Article, Beff should have appeared as a vector. These errors have been corrected in all versions of the Article.

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Acknowledgements

We thank M. Kohda, Y. Tokura and A. Tsukazaki for stimulating discussions. This research was partly supported by the Strategic International Collaborative Research Program (SICORP), Japan Science and Technology Agency, Grant-in-Aid for Scientific Research (S) (No. 21224009), for Specially Promoted Research (No. 25000003) and the ‘Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program)’ from JSPS, Japan. S.W. and X.X. are supported by the US DoE, BES, Division of Materials Sciences and Engineering (DE-SC0008145).

Author information

Affiliations

  1. Quantum-Phase Electronics Center and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan

    • Hongtao Yuan
    • , Mohammad Saeed Bahramy
    • , Kazuhiro Morimoto
    • , Hidekazu Shimotani
    • , Ryuji Suzuki
    • , Ryotaro Arita
    • , Naoto Nagaosa
    •  & Yoshihiro Iwasa
  2. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA

    • Hongtao Yuan
  3. RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan

    • Mohammad Saeed Bahramy
    • , Kentaro Nomura
    • , Bohm-Jung Yang
    • , Ryotaro Arita
    • , Naoto Nagaosa
    •  & Yoshihiro Iwasa
  4. Department of Physics, University of Washington, Seattle, Washington 98195, USA

    • Sanfeng Wu
    •  & Xiaodong Xu
  5. Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

    • Kentaro Nomura
  6. Department of Physics, Tohoku University, Sendai 980-8578, Japan

    • Hidekazu Shimotani
  7. School of Materials Science and Engineering, Nanyang Technological University, 639-798, Singapore

    • Minglin Toh
    •  & Christian Kloc
  8. Department of Material Science and Engineering, University of Washington, Seattle, Washington 98195, USA

    • Xiaodong Xu

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Contributions

H.Y., M.S.B. and K.M. contributed equally to this work. H.Y., M.S.B., R.A. and Y.I. conceived and designed the experiments and theoretical calculation. H.Y. performed the planning, sample fabrication, cryogenic transport measurements and data analysis. M.S.B. and R.A. performed all DFT calculations and data analyses. S.W. and X.X. performed all optical measurement and related data analyses. K.M and H.S. assisted with EDLT device fabrication, transport measurements and data analyses. K.N. and B-J.Y. assisted with the analysis of magnetotransport data. M.T. and C.K. grew the pristine WSe2 single crystals. N.N. and Y.I. led experiments and physical discussions. H.Y., M.S.B. and Y.I. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Hongtao Yuan or Mohammad Saeed Bahramy or Yoshihiro Iwasa.

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DOI

https://doi.org/10.1038/nphys2691

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