Experimental observations and density functional simulations on the structural transition behavior of a two-dimensional transition-metal dichalcogenide

W Liu,L Lin,X X Hu,C Zhang,L J Liu,J B Cao,Z Duan

doi:10.1038/s41598-020-75240-0

Abstract

In this work, we show an obvious evidence of nondestructive Raman spectra for the structural transition, i.e., the existence of a charge density wave (CDW) in monolayer 2H-TaS2, which can exhibit a much higher transition temperature than bulk and results in additional vibrational modes, indicating strong interactions with light. Furthermore, we reveal that the degenerate breath and wiggle modes of 2H-TaS2 originated from the periodic lattice distortion can be probed using the optical methods. Since recently several light-tunable devices have been proposed based on the CDW phase transition of 1 T-TaS2, our study and in particular, the theoretical results will be very helpful for understanding and designing electronic devices based on the CDW of 2H-TaS2.

Highlights

In this work, we show an obvious evidence of nondestructive Raman spectra for the structural transition, i.e., the existence of a charge density wave (CDW) in monolayer 2H-TaS2, which can exhibit a much higher transition temperature than bulk and results in additional vibrational modes, indicating strong interactions with light
A new peak appears at 155 cm−1 below transition temperature, which corresponds to the breath mode and wiggle mode of the CDW of 2H-TaS2, suggesting that the charge density wave transition and periodic lattice distortion can be probed and determined by optical methods, such as temperature dependent Raman scattering
Bulk 2H-TaS2 undergoes a phase transition at 75 K and the distorted CDW phase is formed below the transition temperature, Tc19

Summary

Introduction

We show an obvious evidence of nondestructive Raman spectra for the structural transition, i.e., the existence of a charge density wave (CDW) in monolayer 2H-TaS2, which can exhibit a much higher transition temperature than bulk and results in additional vibrational modes, indicating strong interactions with light. Charge density waves (CDW), structural transitions from a normal to a distorted phase, have been extensively studied for many d ecades[1]. A new peak appears at 155 cm−1 below transition temperature, which corresponds to the breath mode and wiggle mode of the CDW of 2H-TaS2, suggesting that the charge density wave transition and periodic lattice distortion can be probed and determined by optical methods, such as temperature dependent Raman scattering

Methods

Results

Conclusion