Experimental Evidence of a Stable 2H Phase on the Surface of Layered 1T′-TaTe2

Abstract

We report on the low-energy electronic structure of tantalum ditelluride (1T′-TaTe2), one of the charge density wave (CDW) materials from the group V transition metal dichalcogenides using angle-resolved photoemission spectroscopy and density functional theory (DFT). We find that the Fermi surface topology of TaTe2 is quite complicated compared to its isovalent compounds such as TaS2, TaSe2, and isostructural compound NbTe2. Most importantly, we discover that the surface electronic structure of 1T′-TaTe2 has more resemblance to the 2H-TaTe2, while the bulk electronic structure has more resemblance to the hypothetical 1T-TaTe2. These experimental observations are thoroughly compared with our DFT calculations performed on 1T-, 2H-, and 2H (monolayer)/1T-TaTe2. We further notice that the Fermi surface topology is temperature independent up to 180 K, confirming that the 2H phase on the surface is stable up to 180 K and the CDW order is not due to the Fermi surface nesting.