SKM 2021 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 15: Many-Body Quantum Dynamics II (joint session DY/TT)
TT 15.6: Talk
Thursday, September 30, 2021, 11:15–11:30, H2
Interplay of thermal and plasmonic THz nonlinearities on graphene — Jeongwoo Han1, Mattew L. Chin2, •Stephan Winnerl3, Thomas E. Murphy2, and Martin Mittendorff1 — 1Department of Physics, University of Duisburg-Essen, 47057 Duisburg, Germany — 2University of Maryland, College Park, MD 20740, United States of America — 3Helmholtz-Zentrum Dresden- Rossendorf, 01328 Dresden, Germany
Due to the linear dispersion, graphene has attracted much attention as a material platform of nonlinear optics, in particular in the infrared regime. While for higher photon energies the nonlinearities are mostly related to interband transitions and Pauli blocking, in the infrared regime intraband and thermal effects dominate. Here we present the experimental evidence of nonlinear THz absorption beyond thermal effects, i.e., plasmonic nonlinearity, by employing polarization-resolved terahertz pump-probe measurements on graphene disks. By varying the polarization between pump and probe beam, i.e., co- and cross-polarized configurations, we observe a significant polarization dependence of the pump-induced change in transmission. To quantitatively analyze this observation, we develop numerical simulation, allowing us to understand the interplay between thermal and plasmonic nonlinearities. While both contribute to the co-polarized configuration, thermal effects dominate the nonlinearity in the cross-polarized configuration.