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

Among the family of transition metal dichalcogenides (TMD), 1T-TaS₂ stands out for several interesting features including a rich charge density wave phase diagram, quantum spin liquid candidacy, and a low temperature Mott insulator phase. Like many TMDs, low-dimensional 1T-TaS₂ has exhibited behaviour differing from the bulk. 1T-TaS₂ is also known to be air-sensitive, and its properties can be impacted by substrate defects, particularly in the few-layer limit. In this talk, I will present scanning near-field optical microscopy (SNOM) data on a few layer thick microcrystal of 1T-TaS₂ that has been encapsulated from both the atmosphere and substrate impurities. By performing a spatial and temperature dependent study, we image the phase transition down to cryogenic temperatures of 50K. In clean regions of the sample, we find an abrupt metal to insulator transition without intermediate phases. 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 on a local level.