Zhang Songtian S, Rajendran Anjaly, Chae Sang Hoon, Zhang Shuai, Pan Tsai-Chun, Hone James C, Dean Cory R, Basov D N
Department of Physics, Columbia University, New York, NY 10027, USA.
Department of Electrical Engineering, Columbia University, New York, NY 10027, USA.
Nanophotonics. 2023 Mar 24;12(14):2841-2847. doi: 10.1515/nanoph-2022-0750. eCollection 2023 Jul.
Among the family of transition metal dichalcogenides, 1T-TaS 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-TaS 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-TaS. We investigate encapsulated air-sensitive 1T-TaS 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-TaS 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.
在过渡金属二硫属化物家族中，1T-TaS因其多种独特的物理性质而脱颖而出，包括丰富的电荷密度波相图、量子自旋液体候选特性以及低温莫特绝缘体相。随着1T-TaS被减薄至几层极限，这种准二维材料中出现了有趣的物理现象。在此，我们使用扫描近场光学显微镜，对几层厚的1T-TaS微晶的相变进行了空间和温度相关的研究。我们研究了在惰性条件下制备的直至低温的封装的对空气敏感的1T-TaS。我们发现在这个几层极限中存在从金属到绝缘体的突然转变。与之前对薄1T-TaS的输运研究（其中电阻率跳跃变得不可检测）以及对未封装样品的空间分辨研究（发现转变是逐渐的、空间不均匀的）相比，我们的结果提供了新的见解。统计分析表明存在双峰高温相和低温相，并且特征相变滞后现象在几层极限下仍然存在。
