Direct observation of spin-polarized bulk bands in an inversion-symmetric semiconductor
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Methods to generate spin-polarized electronic states in non-magnetic solids are strongly desired to enable all-electrical manipulation of electron spins for new quantum devices1. This is generally accepted to require breaking global structural inversion symmetry1, 2, 3, 4, 5. In contrast, here we report the observation from spin- and angle-resolved photoemission spectroscopy of spin-polarized bulk states in the centrosymmetric transition-metal dichalcogenide WSe2. Mediated by a lack of inversion symmetry in constituent structural units of the bulk crystal where the electronic states are localized6, we show how spin splittings up to ∼0.5 eV result, with a spin texture that is strongly modulated in both real and momentum space. Through this, our study provides direct experimental evidence for a putative locking of the spin with the layer and valley pseudospins in transition-metal dichalcogenides7, 8, of key importance for using these compounds in proposed valleytronic devices.
Riley , J M , Mazzola , F , Dendzik , M , Michiardi , M , Takayama , T , Bawden , L , Granerød , C , Leandersson , M , Balasubramanian , T , Hoesch , M , Kim , T K , Takagi , H , Meevasana , W , Hofmann , P , Bahramy , M S , Wells , J W & King , P 2014 , ' Direct observation of spin-polarized bulk bands in an inversion-symmetric semiconductor ' Nature Physics , vol 10 , no. 11 , pp. 835–839 . DOI: 10.1038/nphys3105
Copyright 2014 The Authors. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://dx.doi.org/10.1038/nphys3105
The authors acknowledge support from the Engineering and Physical Sciences Research Council, UK, the VILLUM foundation, the Calipso program, TRF-SUT Grant RSA5680052 and NANOTEC, Thailand through the CoE Network. P.D.C.K. acknowledges support from the Royal Society through a University Research Fellowship. M.S.B. was supported by a Grant-in-Aid for Scientific Research (S) (No. 24224009) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan.
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