Distinct surface and bulk charge density waves in ultrathin 1T-Ta S2
Physical Review B - Condensed Matter and Materials Physics
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.
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UNI ScholarWorks, Rod Library, University of Northern Iowa
He, Rui; Ye, Zhipeng; Ye, Gaihua; Anderson, Heidi; Dai, Xia; Wu, Xianxin; Hu, Jiangping; Liu, Yu; Lu, Wenjian; Sun, Yuping; Pasupathy, Abhay N.; and Tsen, Adam W., "Distinct surface and bulk charge density waves in ultrathin 1T-Ta S2" (2016). Faculty Publications. 1156.