Regensburg 2022 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 7: 2D Materials 2 (joint session HL/CPP/DS)
DS 7.10: Vortrag
Montag, 5. September 2022, 17:45–18:00, H36
Terahertz free carrier absorption to modulate the optical properties of nanometer-thick van der Waals semiconductors — •Tommaso Venanzi1,2, Malte Selig3, Alexej Pashkin2, Stephan Winnerl2, Manuel Katzer3, Himani Arora2, Artur Erbe2, Amalia Patane4, Zakhar R. Kudrynskyi4, Zakhar D. Kovalyuk5, Leonetta Baldassarre1, Andreas Knorr3, Manfred Helm2, and Harald Schneider2 — 1Sapienza University of Rome, 00185 Rome, Italy — 2Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany — 3Technical University Berlin, 10623 Berlin, Germany — 4University of Nottingham, Nottingham NG7 2RD, UK — 5The National Academy of Sciences of Ukraine, 58001 Chernivtsi, Ukraine
Free carriers in doped semiconductors absorb terahertz radiation when the frequency of the electromagnetic field is lower or comparable to the plasma frequency of the system. This phenomenon can be used to manipulate the optical response of the material. We present here the results of two different experiments performed at the infrared free-electron laser FELBE on atomically-thin van der Waals semiconductors. In MoSe2 monolayers, we observe a terahertz-induced redshift of the trion resonance. Terahertz absorption induces an average high momentum to the carriers and this momentum gets transferred during the trion formation, resulting in a net redshift in the absorption. In few-layer InSe, the terahertz pulses induce a transient quenching of the photoluminescence emission. In both cases, a microscopic study of the hot carrier distribution cooling is also presented.