Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 29: Poster: 2D Materials

O 29.19: Poster

Dienstag, 19. März 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