Journal
2D MATERIALS
Volume 7, Issue 4, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/2053-1583/abae7a
Keywords
transition metal dichalcogenide; bulk and monolayer tite(2); charge density wave; anharmoncity; thickness dependence; phonons
Categories
Funding
- PRACE [2017174186]
- IDRIS
- CINES
- TGCC [91202]
- European Union [881603]
- Agence nationale de la recherche [ANR-19-CE24-0028]
- MIUR PRIN-2017 program [2017Z8TS5B]
- Agence Nationale de la Recherche (ANR) [ANR-19-CE24-0028] Funding Source: Agence Nationale de la Recherche (ANR)
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Most metallic transition metal dichalcogenides undergo charge density wave (CDW) instabilities with similar or identical ordering vectors in bulk and in single layer, albeit with different critical temperatures. Metallic 1 T-TiTe(2)is a remarkable exception as it shows no evidence of charge density wave formation in bulk, but it displays a stable 2 x 2 reconstruction in single-layer form. The mechanism for this 3D-2D crossover of the transition is still unclear, although strain from the substrate and the exchange interaction have been pointed out as possible formation mechanisms. Here, by performing non-perturbative anharmonic calculations with gradient corrected and hybrid functionals, we explain the thickness behaviour of the transition in 1 T-TiTe. We demonstrate that the CDW in single-layer TiTe(2)occurs from the interplay of non-perturbative anharmonicity and an exchange enhancement of the electron-phonon interaction, larger in the single layer than in the bulk. Finally, we study the electronic and structural properties of the single-layer CDW phase and provide a complete description of its electronic structure, phonon dispersion as well as infrared and Raman active phonon modes.
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