Nano-infrared imaging of metal insulator transition in few-layer 1T-TaS₂

• Main Authors: Zhang, Songtian S., Rajendran, Anjaly, Chae, Sang Hoon, Zhang, Shuai, Pan, Tsai-Chun, Hone, James C., Dean, Cory R., Basov, D. N.
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2023
• Subjects: Engineering::Electrical and electronic engineering; Phase Transition; Transition Metal Dichalcogenides
• Online Access: https://hdl.handle.net/10356/169653
• Institution: Nanyang Technological University

Among the family of transition metal dichalcogenides, 1T-TaS2 stands out for several peculiar physical properties including a rich charge density wave phase diagram, quantum spin liquid candidacy and low temperature Mott insulator phase. As 1T-TaS2 is thinned down to the few-layer limit, interesting physics emerges in this quasi 2D material. Here, using scanning near-field optical microscopy, we perform a spatial- and temperature-dependent study on the phase transitions of a few-layer thick microcrystal of 1T-TaS2. We investigate encapsulated air-sensitive 1T-TaS2 prepared under inert conditions down to cryogenic temperatures. We find an abrupt metal-to-insulator transition in this few-layer limit. Our results provide new insight in contrast to previous transport studies on thin 1T-TaS2 where the resistivity jump became undetectable, and to spatially resolved studies on non-encapsulated samples which found a gradual, spatially inhomogeneous transition. A statistical analysis suggests bimodal high and low temperature phases, and that the characteristic phase transition hysteresis is preserved down to a few-layer limit.