Coherent control of phonon anharmonicity

by Dr. Alon Ron

Tel-Aviv University

at Physics Colloquium

Tue, 17 Dec 2024, 12:00
Ilse Katz Institute for Nanoscale Science & Technology (51), room 015

Abstract

Anharmonic lattice vibrations play a key role in many physical phenomena. They govern the heat conductivity of solids, strongly affect the phonon spectra, play a prominent role in soft mode phase transitions, allow ultrafast engineering of material properties, and more. The most direct evidence for anharmonicity is to measure the oscillation frequency changing as a function of the oscillation amplitude. For lattice vibrations, this is not a trivial task, and anharmonicity is probed indirectly through its effects on thermodynamic properties and spectral features or through coherent decay of one mode to another. However, measurement of the anharmonicity of a single Raman mode is still lacking. We show that ultrafast double pump-probe spectroscopy could be used to directly observe frequency shifts of Raman phonons as a function of the oscillation amplitude and disentangle contributions from quasi-harmonic sources such as temperature and changes to the carrier density in the thermoelectric material SnTe. Our results have dramatic implications for the material engineering of future thermoelectrics. Moreover, our methodology could be used to isolate the basic mechanisms driving optically induced phase transitions and other nonlinear phenomena.

Created on 27-10-2024 by Maniv, Eran (eranmaniv)
Updaded on 04-12-2024 by Maniv, Eran (eranmaniv)