Electronic structure of single layer 1T-NbSe${}_2$: interplay of lattice distortions, non-local exchange, and Mott-Hubbard correlations

Abstract

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${}_2$.

arXiv comment10 pages, 11 figures

References in corpus (24)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Two-Dimensional Gas of Massless Dirac Fermions in Graphene
• Atomically thin MoS2: A new direct-gap semiconductor
• Phonons and related properties of extended systems from density-functional perturbation theory
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Wannier90: A Tool for Obtaining Maximally-Localised Wannier Functions
• Continuous-time Monte Carlo methods for quantum impurity models
• Superconductivity in single-layer films of FeSe with a transition temperature above 100 K
• Strongly enhanced charge-density-wave order in monolayer NbSe${}_2$
• Gate-tunable Phase Transitions in 1T-TaS${}_2$
• Characterization of collective ground states in single-layer NbSe2
• Ab initio calculations of quasiparticle band structure in correlated systems: LDA++ approach
• First-principles Calculations of the Electronic Structure and Spectra of Strongly Correlated Systems: Dynamical Mean-field Theory
• Exact, Complete, and Universal Continuous-Time Worldline Monte Carlo Approach to the Statistics of Discrete Quantum Systems
• Gate-induced Superconductivity in atomically thin MoS2 crystals
• Unfolding spinor wavefunctions and expectation values of general operators: Introducing the unfolding-density operator
• Effect of dimensionality on the charge-density-wave in few-layers 2H-NbSe${}_2$
• Three Dimensional Metallic and Two Dimensional Insulating Behavior in Tantalum Dichalcogenides
• Zone-center phonons of bulk, few-layer, and monolayer 1T-TaS${}_2$: Detection of the commensurate charge density wave phase through Raman scattering
• Conserved quantities of SU(2)-invariant interactions for correlated fermions and the advantages for quantum Monte Carlo simulations
• Wannier Function Approach to Realistic Coulomb Interactions in Layered Materials and Heterostructures
• Worm Improved Estimators in Continuous-time Quantum Monte Carlo
• Continuous-time Quantum Monte Carlo using Worm Sampling
• Theoretical description of time-resolved pump/probe photoemission in TaS\_2: a single-band DFT+DMFT(NRG) study within the quasiequilibrium approximation

Cited by in corpus (12)

• Robust charge-density wave strengthened by electron correlations in monolayer 1T-TaSe2 and 1T-NbSe2
• Monolayer 1T-NbSe2 as a 2D correlated magnetic insulator
• Direct identification of Mott Hubbard band pattern beyond charge density wave superlattice in monolayer 1T-NbSe2
• Strength of effective Coulomb interaction in two-dimensional transition-metal Halides MX${}_2$ and MX${}_3$ (M=Ti, V, Cr, Mn, Fe, Co, Ni; X=Cl, Br, I)
• Charge density wave and spin $1/2$ insulating state in single layer 1T-NbS${}_2$
• Ab initio calculation of the effective Coulomb interactions in MX2 (M=Ti, V, Cr, Mn, Fe, Co, Ni; X=S, Se, Te): intrinsic magnetic ordering and Mott insulating phase
• Nonconventional screening of Coulomb interaction in two-dimensional semiconductors and metals: A comprehensive cRPA study of MX2 (M=Mo, W, Nb, Ta; X=S, Se, Te)
• Strain-induced stripe phase in charge ordered single layer NbSe${}_2$
• A Unified Picture of Lattice Instabilities in Metallic Transition Metal Dichalcogenides
• Probing the interlayer coupling in 2$H$-NbS${}_2$ via soft x-ray angle-resolved photoemission spectroscopy
• Controlling magnetic frustration in 1T-TaS${}_2$ via Coulomb engineered long-range interactions
• Dual-space cluster-diagrammatic approach to nonlocal electronic correlations