Hidden CDW states and insulator-to-metal transition after a pulsed femtosecond laser excitation in layered chalcogenide 1T-TaS_{2- x} Se _x.

ABSTRACT: The hidden (H) quantum state in 1T-TaS₂ has sparked considerable interest in the field of correlated electron systems. Here, we investigate ultrafast switches to stable H charge density wave (H-CDW) states observed in 1T-TaS_2-x Se _x , with x = 0 and 0.5 crystals, upon excitation with a single femtosecond laser pulse. In situ cooling transmission electron microscopy observations, initiated by a single femtosecond laser pumping with a low fluence, reveal a clear transition from a commensurate CDW phase (q_C) to a new CDW order with q_H = (1 - ?)q_C for the H-CDW state (? = 1/9) accompanied by an evident phase separation. H-CDW domain relaxation then occurs and yields a stable metallic phase under a high-fluence excitation. Furthermore, electrical resistivity measurements show that the notable drop in x = 0 and 0.5 samples associated with the appearance of H-CDW states depend on laser fluence and temperature. These results potentially provide a new perspective on the photodoping mechanism for the emergence of H-CDW states in the 1T-TaS_2-x Se _x family.

SUBMITTER: Sun K 

PROVIDER: S-EPMC6054513 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature