Charge density wave and atomic trimerization in layered transition-metal dichalcogenides 1T-MX₂materials

¹ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences - Beijing 100190, China
² School of Physical Sciences, University of Chinese Academy of Sciences - Beijing 100049, China
³ Yangtze River Delta Physics Research Center Co., Ltd. - Liyang, Jiangsu, 213300, China
⁴ Songshan Lake Materials Laboratory - Dongguan, Guangdong, 523808, China

^(a) ljq@iphy.ac.cn (corresponding author)

Received: 6 April 2020
Accepted: 27 April 2020

Abstract

In this work, structural investigation and physical measurements of layered transition-metal dichalcogenides (TMDs) 1T-MX₂materials revealed a series of remarkable phenomena in correlation with structural transitions. Our results show that notable structural transformations, such as charge density wave (CDW) transitions, atomic ordering, and micro-twinning could be introduced via chemical substitution in 1T-MX₂. It was demonstrated that substitution of S by Se in 1T-TaS_2-xSe_x resulted in clear changes in the incommensurability of the CDW state; substitution of Se by Te could destruct the CDW state and yield atomic ordering with visible trimerization of the metallic ions. Furthermore, these structural changes yielded a monoclinic stacking along the c-axis direction. Additionally, on substitution of the metal atoms in 1-MX₂, e.g., 1-NbTe₂, structural distortion in the a –b plane could clearly be observed, and high-density twinning lamella often appeared in the crystals because of enhanced intralayer structural deformation. These phase transitions and their relevant structural features could primarily be corelated with alteration of the superconductivity and other physical properties.