Hidden CDW states and insulator-to-metal transition after a pulsed femtosecond laser excitation in layered chalcogenide 1T-TaS<sub>2- <i><sub>x</sub></i></sub> Se <sub><i><sub>x</sub></i></sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 30035223.
- Also identified by DOI 10.1126/sciadv.aas9660 and PMC identifier 6054513.
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Abstract
The hidden (H) quantum state in 1T-TaS<sub>2</sub> 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<sub>2-<i>x</i></sub> Se <sub><i>x</i></sub> , with <i>x</i> = 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 (<i>q</i><sub>C</sub>) to a new CDW order with <i>q</i><sub>H</sub> = (1 - δ)<i>q</i><sub>C</sub> for the H-CDW state (δ = 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 <i>x</i> = 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<sub>2-<i>x</i></sub> Se <sub><i>x</i></sub> family.