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Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 29: Poster: 2D Materials

O 29.19: Poster

Tuesday, March 19, 2024, 12:30–14:30, Poster A

Ultrafast spin dynamics and their layer-specific spin polarization of conduction band electrons in pristine and Cs-doped WSe2 — •Sebastian Hedwig, Gregor Zinke, Benito Arnoldi, Benjamin Stadtmüller, and Martin Aeschlimann — Department of Physics and Research Center OPTIMAS, RPTU Kaiserslautern-Landau, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern, Germany

Layered 2D Van-der-Waals systems are a highly intriguing class of low-dimensional materials with promising spin functionalities for future nanoscale spintronic applications. A particularly interesting member of this class of materials are WSe2 bulk crystals with their hidden spin polarization. These centrosymmetric bulk crystals exhibit an overall spin degenerate band structure while each individual layer is characterized by spin-split valence bands. We conduct time-, spin- and angle-resolved photoemission experiments to study the optically excited spin carrier dynamics at the K- and Σ-points of WSe2. The high surface sensitivity of the photoemission experiments allows us to disentangle the spin polarization of the bands in the first WSe2 layer. After an initial spin-selective excitation at the K-point, which depends on the pump light polarization [1], we observe a subsequent intraband scattering from the K- to the Σ-point of the WSe2 conduction band. This intraband scattering leads to a time-dependent change in the spin polarization of the carriers at the Σ-point. We compare the optically generated spin-dependent carrier population at the Σ-point with that one of Cs-doped WSe2 for which the conduction band valley at the Σ-point is fully occupied. [1] Phys. Rev. Lett. 117, 277201 (2016)

Keywords: WSe2; spin-resolved; time-resolved; ARPES

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