Novel hysteresis effects in the charge density wave compound 1T-TaS_2-xSe_x

The metallic transition metal dichalcogenide (TMD) compound 1T-TaS_2-xSe_x (x = 0 to 2) has been the focus of intense research due to its extremely rich phase diagram as a function of chalcogen doping x. At low temperatures, a variety of strongly correlated phases are observed including commensurate and incommensurate charge density waves (CDWs), superconductivity, and a Mott insulating state. This is particularly interesting as both TaS₂ and TaSe₂ have very similar crystal structure and CDW superstructures, yet exhibit dramatically different electronic properties.

We have prepared single crystals of 1T-TaS_1.2Se_0.8 using chemical vapour transport, and confirmed their quality using EDX and Raman spectroscopy. Electrical transport measurements show CDW phases of varying commensurability and a novel hysteresis effect in resistance that is revealed through a series of cooldown and warm-up cycles. The crucial importance of cooling rate and thickness dependence to these transitions will be discussed.