Coupled vibrational modes in organic crystals
Omer Yaffe a
a Weizmann Institute of Science, Herzl St. 234, Rehovot 7610001, Israel
Invited Speaker Session, Omer Yaffe, presentation 147
Publication date: 6th February 2024

The phenomenon of mode coupling holds significance across various domains of solid-state physics. In the context of organic crystals, understanding the implications of coupled lattice modes is crucial for unraveling the mechanisms behind phase transformations and electron-phonon interactions. In my talk, I will explore how the coupling between vibrational modes is evident in inelastic light scattering. Through experimental case studies, I will illustrate how employing mode coupling models in analyzing Raman spectra enables us to shed light on critical phenomena, such as how a phase transition arises from the thermal population of vibrational states.

In the initial segment of my talk, I will demonstrate that the polarization dependence of Raman scattering in organic crystals at finite temperatures necessitates a description through a fourth-rank tensor formalism. This expansion beyond the conventional second-rank Raman tensor is represented by off-diagonal components in the crystal self-energy on the light scattering process. In the latter part, I will discuss the temperature-dependent evolution of vibrational modes in α α-glycine crystals. Despite its straightforward structure and the absence of known phase transitions, I will present evidence of a phase transition manifesting within the vibrational modes closely associated with the potential surface of its hydrogen bonds.


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