Regensburg 2022 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 25: Poster 1

HL 25.5: Poster

Mittwoch, 7. September 2022, 18:00–20:00, P2

Nonlinear spectroscopy of valley polarization in transition metal dichalcogenides — •Paul Herrmann1, Sebastian Klimmer1, and Giancarlo Soavi1,21Institute of Solid State Physics, Friedrich Schiller University Jena, Jena, Germany — 2Abbe Center of Photonics, Friedrich Schiller University Jena, Jena, Germany

Valleytronics is the branch of science that aims at controlling the valley (i.e., local maximaminima in the valenceconduction bands) degree of freedom to store, manipulate and read information. Monolayer transition metal dichalcogenides (TMDs) are promising candidates for valleytronic applications their hexagonal symmetry in the real and reciprocal space leads to the appearance of two energetically degenerate but non-equivalent valleys at the K and -K points. In addition, their direct bandgap nature in the monolayer limit enables direct optical excitation into these valleys, which can be achieved in a highly selective fashion by means of circularly polarized light [1]. All-optical control of the valley population would enable information processing at optical frequencies, thus overcoming by three to six orders of magnitude the speed of current electronic devices [2]. Here, we perform non-linear and time-resolved optical spectroscopy to study the purity and temporal evolution of the valley population in TMDs. In particular, we combine 2-photon-photoluminescence and time-resolved second harmonic measurements to investigate the impact of intra-valley relaxation and inter-valley scattering on the degree of valley polarization.
[1] Xu X. et al., NPhys 10, 5 (2014) 343-350
[2] Mitchell Waldrop M. et al. Nature 530, (2016) 144-147

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