Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 39: Poster III

HL 39.10: Poster

Wednesday, March 19, 2025, 15:00–18:00, P3

Intensity-dependence of the excitonic third-harmonic generation in bilayer MoS2 — •Ruixin Zuo¹, Matthias Reichelt¹, Cong Ngo¹, Xiaohong Song², and Torsten Meier¹ — ¹Department of Physics, Paderborn University, D-33098 Paderborn, Germany — ²School of Physics and Optoelectronic Engineering, Hainan University, Haikou 570288, China

The large exciton binding energies make layered transition metal dichalcogenides an ideal platform for exploring exciton physics in two-dimensional systems. We numerically and theoretically investigate three-photon transitions to the excitonic states in a bilayer MoS2 and demonstrate that beyond the linear order intraband transitions dominate over interband transitions. Beyond the perturbative limit, transitions to and from the continuum that represent fifth- and higher-order nonlinearities contribute to the excitonic response at the third harmonic where they destructively interfere with the third-order excitations. Applying an in-plane static electric field characteristically modifies the k-resolved fourth-order and higher-order nonlinearities and accordingly the interference at the excitonic resonance. We demonstrate that the yield of the third harmonic generation may rise with increasing static field strength. This finding can be interpreted to arise from a shift from destructive to constructive interference between the lowest- and higher-order excitations. Exciton ionization prevails at even higher static field strengths and results in a decrease of the third harmonic generation.

Keywords: exciton; transition metal dichalcogenides; third harmonic generation; Coulomb interaction