Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 57: 2D Materials beyond Graphene: TMDCs, Slicene and Relatives
O 57.1: Vortrag
Mittwoch, 18. März 2015, 15:00–15:15, MA 005
Imaging spin-valley-layer locking in a transition-metal dichalcogenide — J.-M. Riley1, F. Mazzola2, M. Dendzik3, M. Michiardi3, T. Takayama4, L. Bawden1, C. Granerød2, M. Leandersson5, T. Balasubramanian5, M. Hoesch6, T. Kim6, H. Takagi4, W. Meevasana7, Ph. Hofmann3, M.-S. Bahramy8, J.-W. Wells2, and •Phil D.C. King1 — 1SUPA, University of St. Andrews, UK — 2Norwegian University of Science and Technology, Norway — 3Aarhus University, Denmark — 4Max Planck Institute for Solid State Research, Germany — 5MAX IV Laboratory, Sweden — 6Diamond Light Source, UK — 7Suranaree University of Technology, Thailand — 8University of Tokyo, Japan
A strong locking between the spin and the valley pseudospin in monolayer transition-metal dichalcogenides (TMDCs) such as MoS2 and WSe2 opens unique potential for their use in novel quantum devices exploiting the valley degree of freedom. Here, using spin- and angle-resolved photoemission spectroscopy, we show that such spin-valley coupling persists in bulk 2H-WSe2 where it becomes further entangled with the layer pseudospin [1]. Enormous spin splittings up to ∼0.5 eV result, despite the centrosymmetric nature of the bulk structure which would conventionally preclude the presence of spin polarised states. We argue these occur here due to local inversion symmetry breaking within constituent sub-units of the bulk unit cell, leading to a spin texture that is strongly modulated in both real and momentum space, and allowing us to directly image TMDC spin-valley-layer locking for the first time. [1] Riley et al., Nature Phys. 10 (2014) 835.