SurfaceScience21 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 22: Poster Session II: New methods II

O 22.3: Poster

Montag, 1. März 2021, 13:30–15:30, P

Frequency and momentum-resolved detection of non-thermal gigahertz phonons with Fano coupling to charge carriers — •Thomas Vasileiadis¹, Heng Zhang², Hai Wang², Mischa Bonn², George Fytas², and Bartlomiej Graczykowski¹ — ¹Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznanskiego 2, 61-614 Poznan, Poland. — ²Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.

Spontaneous micro-Brillouin light scattering (µ-BLS) can probe gigahertz acoustic phonons in nano-confined materials with momentum and spatial resolution. However, the downsizing of the scattering volume implies weak BLS signals, sample overheating, and damage [1]. In this work, we present pumped-BLS [2], an all-optical technique that generates non-thermal acoustic phonons with ultrashort laser pulses and probes them with frequency- and momentum-resolution. Using pumped-BLS we show: (i) a hundred-fold enhancement of BLS spectra, compared to equilibrium, of 260 nm thick Si membranes due to photoexcited non-thermal gigahertz phonons, (ii) Stokes / anti-Stokes asymmetry due to asymmetric non-thermal phonon propagation and (iii) strongly asymmetric Fano resonances due to coupling between the electron-hole pairs and the phonons. This project is funded from NCN (UMO-2018/31/D/ST3/03882), ERC (grant no. 694977) and FNP (POIR.04.04.00-00-5D1B/18). TV acknowledges funding from the European Union’s Horizon 2020 research and innovation programme. [1] M. Sledzinska, et al. Adv. Funct. Mater. 30 (8), 2020. [2] Th. Vasileiadis et al. Science Advances 6 (51), eabd4540, 2020.