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arXiv · 1408.6778

Direct observation of spin-polarised bulk bands in an inversion-symmetric semiconductor

J. M. Riley·F. Mazzola·M. Dendzik·M. Michiardi·T. Takayama·L. Bawden·C. Granerød·M. Leandersson·T. Balasubramanian·M. Hoesch·T. K. Kim·H. Takagi·W. Meevasana·Ph. Hofmann·M. S. Bahramy·J. W. Wells·P. D. C. King
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Abstract

Methods to generate spin-polarised electronic states in non-magnetic solids are strongly desired to enable all-electrical manipulation of electron spins for new quantum devices. This is generally accepted to require breaking global structural inversion symmetry. In contrast, here we present direct evidence from spin- and angle-resolved photoemission spectroscopy for a strong spin polarisation of bulk states in the centrosymmetric transition-metal dichalcogenide WSe$_2$. We show how this arises due to a lack of inversion symmetry in constituent structural units of the bulk crystal where the electronic states are localised, leading to enormous spin splittings up to $\sim\!0.5$ eV, with a spin texture that is strongly modulated in both real and momentum space. As well as providing the first experimental evidence for a recently-predicted `hidden' spin polarisation in inversion-symmetric materials, our study sheds new light on a putative spin-valley coupling in transition-metal dichalcogenides, of key importance for using these compounds in proposed valleytronic devices.

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J. M. Riley, F. Mazzola, M. Dendzik, M. Michiardi, T. Takayama, L. Bawden, C. Granerød, M. Leandersson, T. Balasubramanian, M. Hoesch, T. K. Kim, H. Takagi, W. Meevasana, Ph. Hofmann, M. S. Bahramy, J. W. Wells, P. D. C. King. 2014-08-28. Direct observation of spin-polarised bulk bands in an inversion-symmetric semiconductor. https://doi.org/10.1038/nphys3105

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