Strain engineering a 4a×√3a charge-density-wave phase in transition-metal dichalcogenide 1T−VSe2
Duming Zhang, Jeonghoon Ha, Hongwoo H. Baek, Yang-Hao Chan, Donat F. Natterer, Alline F. Myers, Joshua D. Schumacher, William G. Cullen, Albert Davydov, Young Kuk, Mei-Yin Chou, Nikolai B. Zhitenev, Joseph A. Stroscio
We report a new charge density wave (CDW) structure in strained 1T-VSe2 thin films synthesized by molecular beam epitaxy. The CDW structure is unconventional and exhibits a rectangular 4a×√3a periodicity, as opposed to the previously reported hexagonal 4a×4a structure in bulk crystals. First-principles calculations find both 4a×4a and 4a×√3a structures resulting from soft modes in the phonon dispersion, with the later structure lowered in energy in the presence of strain. A CDW energy gap of 2Δ_"CDW" =(9.1±0.1) "meV" was determined that evolved into a larger metal-insulator gap at temperatures below 500 mK.