Pressure-induced phonon frequency shifts in transition-metal nitrides

TL;DR

This study investigates how high pressure affects phonon spectra in transition-metal nitrides ZrN, HfN, and NbN using Raman scattering, revealing shifts in phonon frequencies that correlate with changes in superconducting transition temperatures.

Contribution

First experimental measurement of pressure-dependent phonon spectra in transition-metal nitrides ZrN, HfN, and NbN using Raman scattering techniques.

Findings

Phonon frequencies increase with pressure in studied nitrides.

Pressure dependence of superconducting transition temperature is explained.

Distinct acoustic and optical phonon bands identified.

Abstract

We report the first experiments on the high pressure phonon spectra of transition-metal nitrides HfN, ZrN, and NbN, obtained by Raman scattering measurements. Two pronounced bands, which are related to the acoustic part at low frequency around 200 cm$^{-1}$ and the optical part at high frequency around 550 cm$^{-1}$ of the phonon spectrum, respectively, shift to high frequency values with increasing pressure. An analysis of the results allows us to reproduce the experimental pressure dependence of the superconducting transition temperature $T_{c}$ of ZrN and NbN.