Distinct surface and bulk charge density waves in ultrathin 1T-Ta S2

Rui He, Zhipeng Ye, Gaihua Ye, Heidi Anderson, Xia Dai, Xianxin Wu, Jiangping Hu, Yu Liu, Wenjian Lu, Yuping Sun, Abhay N. Pasupathy, Adam W. Tsen

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37 Scopus citations


We employ low-frequency Raman spectroscopy to study the nearly commensurate (NC) to commensurate (C) charge density wave (CDW) transition in 1T-TaS2 ultrathin flakes protected from oxidation. We identify additional modes originating from C-phase CDW phonons that are distinct from those seen in bulk 1T-TaS2. We attribute these to CDW modes from the surface layers. By monitoring individual modes with temperature, we find that surfaces undergo a separate, low-hysteresis NC-C phase transition that is decoupled from the transition in the bulk layers. This indicates the activation of a secondary phase nucleation process in the limit of weak interlayer interaction, which can be understood from energy considerations.

Original languageEnglish
Article number201108
JournalPhysical Review B
Issue number20
StatePublished - Jan 1 2016


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