Raman scattering in osmium under pressure

TL;DR

This study investigates how pressure and temperature affect the Raman-active phonon mode of osmium, revealing non-adiabatic electron-phonon interactions and sensitivity to shear stress up to 20 GPa.

Contribution

It provides new insights into pressure and temperature effects on osmium's phonon modes, emphasizing non-adiabatic effects and stress sensitivity.

Findings

Phonon frequency increases with pressure at 0.73(5) cm^{-1}/GPa.

Temperature induces a significant, wavelength-dependent phonon shift.

Phonon line width increases upon cooling, indicating non-adiabatic effects.

Abstract

The effect of pressure and temperature on the Raman-active phonon mode of osmium metal has been investigated for pressures up to 20 GPa and temperatures in the range 10--300 K. Under hydrostatic conditions (He pressure medium) the phonon frequency increases at a rate of 0.73(5) cm^{-1}/GPa (T = 300 K). A large temperature-induced and wavelength-dependent frequency shift of the phonon frequency is observed, of which only a small fraction can be associated with the thermal volume change. The main contribution to the temperature dependence of the phonon frequency is rather attributed to non-adiabatic effects in the electron-phonon interaction, which explains also the observation of an increasing phonon line width upon cooling. The phonon line width and the pressure-induced frequency shift were found to be unusually sensitive to shear stress.