Resonance-Induced Anomalies in Temperature-Dependent Raman Scattering of PdSe$_{2}$

TL;DR

This study investigates the temperature-dependent Raman spectra of PdSe₂, revealing resonance effects and phonon interactions that influence its vibrational properties, with implications for optoelectronic applications.

Contribution

It provides the first comprehensive analysis of resonance-induced anomalies in PdSe₂'s Raman spectra across a wide temperature range, supported by DFT calculations.

Findings

Enhanced out-of-plane phonon mode at 120 K

Suppressed in-plane phonon modes at 120 K

Nonlinear phonon frequency shifts indicating phonon decay

Abstract

We report a comprehensive Raman study of the phonon behaviour in PdSe$_2$ in the temperature range of 5 K to 300 K. A remarkable change in the Raman spectrum is observed at 120 K: a significant enhancement of the out-of-plane phonon A$^{1}_{g}$ mode, accompanied by a suppression of the in-plane A$^{2}_{g}$ and B$^{2}_{1g}$ modes. This intriguing behavior is attributed to a temperature-dependent resonant excitation effect. The results are supported by density functional theory (DFT) calculations, which demonstrate that the electron-phonon coupling for the phonon modes varies and is strongly associated with the relevant electronic states. Furthermore, nonlinear frequency shifts are identified in all modes, indicating the decay of an optical phonon into multiple acoustic phonons. The study of Raman emission reported here, complemented by linear optical spectroscopy, reveals an unexpected scenario for the vibrational properties of PdSe$_2$ that holds substantial promise for future applications in PdSe$_2$-based optoelectronics.