Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 11: Electronic Structure of Surfaces: Spectroscopy, Surface States I

O 11.12: Vortrag

Montag, 17. März 2025, 17:45–18:00, H4

Broadband THz Non-Linear Response In Topological Noble Metal Dichalcogenides — George de Coster^1,2, Lucas Lafeta³, Stefan Heiserer¹, Zdeněk Sofer⁴, Achim Hartschuh³, Georg Duesberg¹, and •Paul Seifert¹ — ¹Institute of Physics, University of the Bundeswehr Munich, EIT, Werner-Heisenberg-Weg. 39, 85577 Neubiberg, Germany — ²DEVCOM Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland, United States — ³Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Butenandtstraße 5-13 (E), 81377 Munich, Germany — ⁴Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic

Noble metal dichalcogenides belong to the material class of layered 2D materials and were shown to host type-II Dirac semi-metallic behavior, as well as topological surface states and superconductivity. Intriguingly, noble metal dichalcogenides display strong second harmonic generation and second order photocurrent response despite their centrosymmetric crystal structure. We investigate the spectrally-resolved optical response and reveal second and third order non-linear response at both, optical frequencies as well as in the THz range. The latter is analyzed in polarization resolved spectroscopy, that points towards spin-polarized bands at the symmetry broken surface as origin of the non-linearities. Our results elucidate the spectral opto- electronic response at low energies and discuss its anisotropy in light of underlying symmetry constraints.

Keywords: Noble Metal Dichalcogenide; Topology; Non-linear; Harmonic Generation; THz