A Raman Probe of Phonons and Electron-phonon Interactions in NbIrTe4

TL;DR

This study uses micro-Raman scattering to investigate phonons and electron-phonon interactions in NbIrTe4, a candidate Weyl semimetal, revealing detailed phonon modes and their energy-dependent coupling characteristics.

Contribution

It provides the first detailed Raman characterization of NbIrTe4's phonon modes and their electron-phonon coupling, supported by theoretical calculations.

Findings

Identified 19 phonon modes and their symmetries.

Demonstrated energy-dependent variation of Raman tensor elements.

Revealed strong electron-phonon coupling variations in NbIrTe4.

Abstract

The semimetal NbIrTe4 has been proposed to be a Type-II Weyl semimetal with 8 pairs of opposite Chirality Weyl nodes which are very close to the Fermi energy. This topological electronic structure is made possible because of the broken inversion symmetry of NbIrTe4 which is an orthorhombic crystal with Td symmetry. Using micro-Raman scattering as a probe, we observe the frequencies and symmetries of 19 phonon modes (ranging from 40 to 260 cm-1) in this material and compare to Density Functional Theory calculations. Using angular and polarization resolved Raman scattering for green (514 nm) and red (633 nm) laser excitation, we show that it is possible to extract the excitation energy dependence of the Raman tensor elements associated with each measurable phonon mode. We show that these tensor elements vary substantially in a small energy range which reflects a strong variation of the electron-phonon coupling for these modes.