Origin Of The Structural Phase Transition In Single-Crystal Tate2

The origin of the structural phase transition of TaTe2 has been investigated through the measurements of the temperature-dependent Raman spectroscopy and first-principles calculations. Based on the experimental and the calculation results, some interpretations are present. Firstly, abnormal redshifts of few Raman peaks are observed around the structural distortion temperature T-S similar to 170 K, which is thought to originate from the clustering of Ta atoms below T-S . Secondly, new modes of Raman spectrum below T-s are present, which is suggested to be related to the possible transition of charge density wave (CDW) in TaTe2 from the room temperature to the low temperature. The ground state of the TaTe2 is the special charge modulation, which is related to the formation of Ta-Ta dimer structure at low temperature. All explanations have been supported by first-principles calculations. Our results suggest that TaTe2 is an alternative platform to explore the charge-lattice coupling with rich structural and charge configurations in MX2 systems, where M is the transition metal ion (Nb, Ta, Mo, etc.) and X is the chalcogenide one (S, Se, or Te).