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Substrate-induced suppression of charge density wave phase in monolayer 1 H − TaS 2 on Au(111)

2019; American Physical Society; Volume: 99; Issue: 17 Linguagem: Inglês

10.1103/physrevb.99.174113

2469-9977

Heraclitos Lefcochilos-Fogelquist, Oliver R. Albertini, Amy Liu,

Electrocatalysts for Energy Conversion

Recent experiments have found that monolayer $1H\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ grown on Au(111) lacks the charge density wave (CDW) instability exhibited by bulk $2H\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$. Additionally, angle-resolved photoemission spectroscopy measurements suggest that the monolayer becomes strongly electron doped by the substrate. While density functional theory (DFT) calculations have shown that electron doping can suppress the CDW instability in monolayer $1H\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$, it has been suggested that the actual charge transfer from the substrate may be much smaller than the apparent doping deduced from photoemission data. We present DFT calculations of monolayer $1H\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ on Au(111) to explore substrate effects beyond doping. We find that the CDW instability is suppressed primarily by strong S-Au interactions rather than by doping. The S-Au interaction results in a structural distortion of the ${\mathrm{TaS}}_{2}$ monolayer characterized by both lateral and out-of-plane atomic displacements and a $7\ifmmode\times\else\texttimes\fi{}7$ periodicity dictated by the commensurate interface with Au. Simulated STM images of this $7\ifmmode\times\else\texttimes\fi{}7$ distorted structure are consistent with experimental STM images. In contrast, we find a robust $3\ifmmode\times\else\texttimes\fi{}3$ CDW phase in monolayer $1H\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ on a graphene substrate with which there is minimal interaction.