Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 76: 2D Materials beyond Graphene: Dynamics and Excitation
O 76.1: Hauptvortrag
Donnerstag, 10. März 2016, 10:30–11:00, S054
Spin- and Pseudospin-Polarized Excited States in bulk WSe2 — Roman Bertoni1, Christopher Nicholson1, Lutz Waldecker1, Michele Puppin1, Claude Monney2, Cephise Cacho3, Hannes Huebener4, Umberto De Giovannini4, Angel Rubio4, Martin Wolf1, and •Ralph Ernstorfer1 — 1Fritz-Haber-Institut der MPG, Berlin, DE — 2University of Zurich, Zurich, CH — 3Rutherford Appleton Laboratory, Didcot, UK — 4University of the Basque Country, San Sebastian, ES
The peculiar electronic structure of layered semiconducting transition metal dichalgogenides (TMDC) like WSe2 gives rise to internal quantum degrees of freedom of the electrons in addition to the spin, namely valley and layer pseudospins. Employing XUV-based time- and angle-resolved photoemission spectroscopy (trARPES) with resonant excitation of excitonic transitions, we observe circular dichroism in the excited state population in the K valleys of the topmost trilayer of bulk WSe2. Such spin-, valley and layer-polarized excitations are a manifestation of broken site symmetry in an inversion-symmetric crystal. The valley- and layer-resolved view on excited state dynamics provided by trARPES is complemented by the investigation of electron-lattice coupling in multilayer WSe2 with femtosecond electron diffraction. Latter studies reveal the dynamics of global energy transfer from electronic to vibrational degrees of freedom in TMDCs subsequent to excitonic as well as interband excitation.