A Raman probe of phonons and electron\u2013phonon interactions in the Weyl semimetal NbIrTe4

Iraj Abbasian Shojaei,Seyyedesadaf Pournia,Brenden R Ortiz,Giriraj Jnawali,Fu-Chun Zhang,Congcong Le,Leigh M Smith,Howard E Jackson,Stephen D Wilson

doi:10.1038/s41598-021-87302-y

Abstract

There is tremendous interest in measuring the strong electron–phonon interactions seen in topological Weyl semimetals. 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. We show using polarized angular-resolved micro-Raman scattering at two excitation energies that we can extract the phonon mode dependence of the Raman tensor elements from the shape of the scattering efficiency versus angle. This van der Waals semimetal with broken inversion symmetry and 24 atoms per unit cell has 69 possible phonon modes of which we measure 19 modes with frequencies and symmetries consistent with Density Functional Theory calculations. 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.

Highlights

There is tremendous interest in measuring the strong electron–phonon interactions seen in topological Weyl semimetals
We show that the observed modes and symmetries are consistent with ab-initio density functional theoretical (DFT) calculations and extract the normal modes of atomic vibrations for these modes
A total of 19 Raman active modes, 13 A 1 and 6 A2 from NbIrTe4 have been detected through angle-resolved polarized micro-Raman scattering for 633 nm and 514 nm excitations

Summary

Introduction

There is tremendous interest in measuring the strong electron–phonon interactions seen in topological Weyl semimetals. We show using polarized angular-resolved micro-Raman scattering at two excitation energies that we can extract the phonon mode dependence of the Raman tensor elements from the shape of the scattering efficiency versus angle This van der Waals semimetal with broken inversion symmetry and 24 atoms per unit cell has 69 possible phonon modes of which we measure 19 modes with frequencies and symmetries consistent with Density Functional Theory calculations. In this paper we use polarized angular-resolved Raman scattering in NbIrTe4, a possible Type II Weyl semimetal, to show that one can extract the Raman tensor elements for each phonon mode from the shape of the scattering efficiency versus angle. While several magneto-transport measurements in late 2019 have shown non saturating magneto-resistance at low temperature, and quantum oscillations[41,42] which are consistent with a complex Fermi surface, there are no angle-resolved photoemission spectroscopy (ARPES) measurements to investigate the expected surface Fermi arcs or band crossings expected in this material

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