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 WSe2. 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 ∼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.
@article{arxiv.1408.6778,
title = {Direct observation of spin-polarised bulk bands in an inversion-symmetric semiconductor},
author = {J. M. Riley and F. Mazzola and M. Dendzik and M. Michiardi and T. Takayama and L. Bawden and C. Granerød and M. Leandersson and T. Balasubramanian and M. Hoesch and T. K. Kim and H. Takagi and W. Meevasana and Ph. Hofmann and M. S. Bahramy and J. W. Wells and P. D. C. King},
journal= {arXiv preprint arXiv:1408.6778},
year = {2022}
}