Dresden 2026 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 3: 2D Materials I – Excitonic properties
HL 3.6: Talk
Monday, March 9, 2026, 10:45–11:00, POT/0081
Signatures of efficient intervalley scattering by acoustic phonons in WSe2 monolayers — •Hendrik Lambers1, Daniel Groll2, Daniel Wigger2, Nihit Saigal1, Lara Blinov1, Tilmann Kuhn2, Alexander W. Holleitner3, and Ursula Wurstbauer1 — 1Institute of Physics, University of Münster — 2Institute of Solid State Theory, University of Münster — 3Walter Schottky Institute, Technical University of Munich
When group VI TMDC are thinned down to the monolayer limit, their bandgap transfers from indirect to direct. While their strong exciton dominated light-matter coupling can be easily investigated by optical spectroscopy, exciton-phonon coupling is often inaccessible, even though it is important for exciton thermalization and intervalley scattering. We employ resonant Raman scattering at cryogenic temperatures to study the exciton phonon coupling in WSe2 monolayers. In resonance with the WSe2 exciton, we observe rich Raman spectra. Here, we focus on the resonance profiles of the degenerated A1’/E’ mode, that exhibits two asymmetric resonance peaks that cannot be described by a first order Raman scattering process. A higher-order Raman scattering process including simultaneous generation and annihilation of acoustic M-point phonons describes the experimental resonance profile well. Our results indicate a strong electron phonon coupling and efficient intervalley scattering between the nearly degenerate direct and indirect exciton transitions in WSe2. The findings are relevant to understand unusual bright emission in WSe2 monolayers despite spin-forbidden lowest interband transition.
Keywords: TMDC; Resonant Raman Spectroscopy; Intervalley scattering; WSe2