Ultrafast optical melting of trimer superstructure in layered 1T′-TaTe2

Quasi-two-dimensional transition-metal dichalcogenides are a key platform for exploring emergent nanoscale phenomena arising from complex interactions. Access to the underlying degrees-of-freedom on their natural time
scales motivates the use of advanced ultrafast probes sensitive to self-organized atomic-scale patterns. The Kaindl group at Lawrence Berkeley National Lab recently reported the ultrafast investigation of 1T’-TaTe2 , demonstrating a rapid picosecond melting of its trimer cluster lattice superstructure in the low temperature (LT) phase. They observed photo-induced melting of the LT order on 1.4 ps timescale, indicative of fast switching, followed by recovery into a hot (3 × 3) trimer phase. Insight into the nature of trimer cluster melting is obtained via density functional calculations, which indicate an initial quench driven by charge-transfer transitions from bonding to non-bonding states of the Ta trimer—suggesting pathways for a photo-induced transition that is unique among the family of TaX2 materials. This work establishes TaTe2 as a promising material for optical control, motivating examination of concomitant electronic dynamics for device applications. Published in Communications Physics 4, 152 (2021).