Electronic structure of single layer 1T-NbSe$_2$: interplay of lattice distortions, non-local exchange, and Mott-Hubbard correlations
| Autor: | Malte Schüler, Gunnar Schönhoff, Tim O. Wehling, E. Kamil, Malte Rösner, Jan Berges, Giorgio Sangiovanni |
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| Rok vydání: | 2018 |
| Předmět: |
Physics
Condensed matter physics Strongly Correlated Electrons (cond-mat.str-el) Phonon FOS: Physical sciences Primitive cell 02 engineering and technology Electronic structure 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Many-body problem Brillouin zone Condensed Matter - Strongly Correlated Electrons Delocalized electron Ab initio quantum chemistry methods 0103 physical sciences General Materials Science Condensed Matter::Strongly Correlated Electrons 010306 general physics 0210 nano-technology Electronic band structure |
| DOI: | 10.48550/arxiv.1804.03898 |
| Popis: | Using ab-initio calculations we reveal the nature of the insulating phase recently found experimentally in monolayer 1T-NbSe$_2$. We find soft phonon modes in a large parts of the Brillouin zone indicating the strong-coupling nature of a charge-density-wave instability. Structural relaxation of a $\sqrt{13}\times\sqrt{13}$ supercell reveals a Star-of-David reconstruction with an energy gain of 60 meV per primitive unit cell. The band structure of the distorted phase exhibits a half-filled flat band which is associated with orbitals that are delocalized over several atoms in each Star of David. By including many-body corrections through a combined GW, hybrid-functional, and DMFT treatment, we find the flat band to split into narrow Hubbard bands. The lowest energy excitation across the gap turns out to be between itinerant Se-$p$ states and the upper Hubbard band, determining the system to be a charge-transfer insulator. Combined hybrid-functional and GW calculations show that long-range interactions shift the Se-$p$ states to lower energies. Thus, a delicate interplay of local and long-range correlations determines the gap nature and its size in this distorted phase of the monolayer 1T-NbSe$_2$. Comment: 10 pages, 11 figures |
| Databáze: | OpenAIRE |
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