Examining Experimental Raman Mode Behavior in Mono- and Bi-layer 2H-TaSe$_{2}$ via Density Functional Theory

TL;DR

This study combines experimental Raman spectroscopy and density functional theory calculations to analyze vibrational modes in mono- and bi-layer 2H-TaSe$_{2}$, revealing insights into interlayer interactions and charge density wave phenomena.

Contribution

It provides a detailed comparison of experimental and theoretical vibrational modes in mono- and bi-layer TaSe$_{2}$, including forbidden and low-frequency modes, advancing understanding of layer-dependent behaviors.

Findings

Excellent match between experimental and DFT-predicted vibrational modes

Identification of forbidden Raman modes and low-frequency CDW modes

Demonstrates the influence of interlayer interactions on vibrational behavior

Abstract

Tantalum diselenide (TaSe$_{2}$) is a metallic transition metal dichalcogenide whose equilibrium structure and vibrational behavior strongly depends on temperature and thickness, including the emergence of charge density wave (CDW) states at very low T. In this work, observed modes for mono- and bi-layer are described across several spectral regions and com-pared to the bulk ones. Such modes, including an experimentally observed forbidden Raman mode and low frequency CDW modes, are then matched to corresponding density functional theory (DFT) predicted vibrations, to unveil their inner working. The excellent match between experimental and computational results justifies the presented vibrational visualizations of these modes. Additional support is provided by experimental phonons seen in Raman spectra as a function of temperature and thickness. These results highlight the importance of understanding interlayer interactions and their effects on mode behaviors.