Investigating phase transitions of the Weyl semimetals (MoTe2 and NbIrTe4) by using Raman spectroscopy and infrared reflected polarized light.

Abstract

Since the discovery of the topological Weyl semimetal phase, these materials have been a major topic for researchers aiming to understand their complex properties. Transition metal dichalcogenides (TMDs), such as NbIrTe4 and MoTe2, have been proposed as Weyl semimetal materials. These materials host Weyl points (Weyl fermions) due to their crystal structure's broken spatial inversion symmetry. As their thickness decreases to a few layers, their crystal structure transitions to a monoclinic phase. This structural change restores inversion symmetry in the thinner layers, opening a gap between the valence and conduction bands. This thesis investigates the phase transition of these materials based on thickness and temperature, specifically focusing on NbIrTe4 and MoTe2. We demonstrate how reflected polarized light can be used to distinguish between different phases. Our findings provide new insights into the electronic structure of topological Weyl semimetals and suggest potential applications in optical and electronic devices.