SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 54: Poster Session IV: Poster to Mini-Symposium: Ultrafast surface dynamics at the space-time limit II
O 54.3: Poster
Dienstag, 2. März 2021, 13:30–15:30, P
Ultrafast hot electron relaxation in a metallic THz-STM junction — •Natalia Martín Sabanés1,2, Faruk Krecinic1, Fabian Schulz1, Chenfang Lin1,3, Takashi Kumagai1,4, Martin Wolf1, and Melanie Müller1 — 1Fritz Haber Institute, Berlin, Germany — 2IMDEA nanoscience, Madrid, Spain — 3College of Materials Science and Engineering, Hunan University, Hunan, China — 4Center for Mesoscopic Sciences, Institute for Molecular Science, Okazaki, Japan
We investigate the ultrafast dynamics of photoexcited hot electrons in a metallic STM junction through modulation of the junction barrier with an ultrabroadband THz field. The ability for phase-resolved quantitative sampling of the THz bias induced in the junction allows to probe the relaxation of hot carriers in the STM on THz sub-cycle time scales. Exact knowledge of the THz voltage is obtained via THz-field-induced modulation of instantaneous photocurrents excited with 8 fs near-infrared (NIR) laser pulses [1-3]. In the presence of a non-instantaneous response, distortions of the original THz waveform occur, from which the ultrafast photocurrent decay can be extracted. Applying a 1D-model for the transmission of thermalized hot electrons to reproduce the distorted THz waveforms, we obtain quantitative information about the electronic temperature in the tip and its ultrafast decay. Our approach provides a new route for non-resonant probing of charge carrier dynamics in photoexcited STM on time scales much shorter than a single THz cycle. [1] L. Wimmer et al., Nat. Phys., 10, 432-436, 2014. [2] M. Müller et al., ACS Photonics, 7(8), 2046-2055, 2020. [3] S. Yoshida et al., ACS Photonics 6, 1356-1364, 2019.