Charge density wave and spin $1/2$ insulating state in single layer 1T-NbS${}_2$

Abstract

In bulk samples and few layer flakes, the transition metal dichalcogenides NbS${}_2$ and NbSe${}_2$ assume the H polytype structure with trigonal prismatic coordination of the Nb atom. Recently, however, single and few layers of 1T-NbSe${}_2$ with octahedral coordination around the transition metal ion were synthesized. Motivated by these experiments and by using first-principles calculations, we investigate the structural, electronic and dynamical properties of single layer 1T-NbS${}_2$. We find that single-layer 1T-NbS${}_2$ undergoes a $\sqrt{13}\times \sqrt{13}$ star-of-David charge density wave. Within the generalized gradient approximation, the weak interaction between the stars leads to an ultraflat band at the Fermi level isolated from all other bands. The spin-polarized generalized gradient approximation stabilizes a total spin $1/2$ magnetic state with opening of a $0.15$ eV band gap and a $0.21{\mu }_B$ magnetic moment localized on the central Nb in the star. Within GGA+U, the magnetic moment on the central Nb is enhanced to $0.41{\mu }_B$ and a larger gap occurs. Most important, this approximation gives a small energy difference between the 1T and 1H polytypes (only $+0.5$ mRy/Nb), suggesting that the 1T-polytype can be synthesized in a similar way as done for single layer 1T-NbSe${}_2$. Finally we compute first and second nearest neighbors magnetic inter-star exchange interactions finding $J_1$=9.5~K and $J_2$=0.4~K ferromagnetic coupling constants.

References in corpus (18)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Two Dimensional Atomic Crystals
• Magic-angle graphene superlattices: a new platform for unconventional superconductivity
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• A linear response approach to the calculation of the effective interaction parameters in the LDA+U method
• Computational 2D Materials Database: Electronic Structure of Transition-Metal Dichalcogenides and Oxides
• Strongly enhanced charge-density-wave order in monolayer NbSe${}_2$
• Characterization of collective ground states in single-layer NbSe2
• Is 1T-TaS${}_2$ a 40 year old quantum spin liquid?
• 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
• Anharmonic suppression of Charge density wave in 2H-NbS${}_2$
• Phonon-assisted magnetic Mott-insulating state in the charge density wave phase of single-layer 1TNbSe2
• Quasi one-dimensional metallic band dispersion in the commensurate charge density wave of $1T$-TaS${}_2$
• Charge-density-wave phase, mottness and ferromagnetism in monolayer $1T$-NbSe${}_2$
• Electronic structure of single layer 1T-NbSe${}_2$: interplay of lattice distortions, non-local exchange, and Mott-Hubbard correlations
• Epitaxial single layer NbS${}_2$ on Au(111): synthesis, structure, and electronic properties

Cited by in corpus (12)

• 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 instability and pressure-induced superconductivity in bulk 1T-NbS2
• 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
• $\text{Ab initio}$ theory of magnetism in two-dimensional $1T$-TaS${}_2$
• Spin-orbit and exchange proximity couplings in graphene/1T-TaS${}_2$ heterostructure triggered by a charge density wave
• Can the "shadow" of graphene band clarify its flatness?
• Stacking effect and Coulomb correlation in layered charge density wave phase of 1T-NbS2
• Superconductivity induced by gate-driven hydrogen intercalation in the charge-density-wave compound 1T-TiSe2
• Unidirectional Kondo scattering in layered NbS2
• Superconductivity and strain-enhanced phase stability of Janus tungsten chalcogenide hydride monolayers
• Charge density wave in single-layer Pb/Ge(111) driven by Pb-substrate exchange interaction
• Theoretical prediction of Structural Stability and Superconductivity in Janus Ti2CSH MXene