Anharmonic Decay of Coherent Optical Phonons in Antimony

TL;DR

This study investigates how coherent optical phonons in antimony decay due to anharmonic interactions, revealing temperature-dependent decay rates, frequency shifts, and amplitude changes explained by phonon-phonon coupling and thermal effects.

Contribution

It provides detailed experimental insights into the anharmonic decay mechanisms of optical phonons in antimony across a wide temperature range, with a model applicable to other metals.

Findings

Decay rate increases with temperature due to phonon-phonon coupling

Phonon frequency decreases with temperature from thermal expansion and anharmonic effects

Amplitude of coherent phonons decreases with temperature, explained by Raman scattering linewidth model

Abstract

Anharmonic decay of coherent optical phonons in semimetal Sb has been investigated by using a femtosecond pump-probe technique. The coherent $A_{1g}$ mode is observed in time domain in a wide temperature range of 7 - 290 K. The decay rate (the inverse of the dephasing time) systematically increases as the lattice temperature increases, which is well explained by anharmonic phonon-phonon coupling, causing decay of the optical phonon into two acoustic phonon modes. The frequency of the $A_{1g}$ mode decreases with the temperature, which is interpreted to the results of both thermal expansion and anharmonic phonon-phonon coupling. The temperature dependence of the amplitude of the coherent $A_{1g}$ mode exhibits a decrease with the lattice temperature, which is well reproduced by considering the peaked intensity of spontaneous Raman scattering assuming a Lorentzian line shape with the linewidth controlled by the anharmonic decay, and this model can be applicable to other metallic system, like Zn.