Mott insulator tuning via structural distortion in monolayer 1T-NbSe2

Abstract

Mott state in 1T-TaS2 is predicted to host quantum spin liquids (QSL). However, its insulating mechanism is controversial due to complications from interlayer coupling. Here, we study the Mott state in monolayer 1T-NbSe2, an electronic analogy to TaS2 exempt from interlayer coupling, using spectroscopic imaging scanning tunneling microscopy and first principles calculations. Monolayer NbSe2 surprisingly displays two types of Star-of-David (SD) motifs with different Mott gap sizes, that are interconvertible via temperature variation. And, bilayer 1T-NbSe2 shows Mott collapse by interlayer coupling. Our calculation unveils the two types of SDs possess distinct structural distortions, altering the effective Coulomb energies of the central Nb orbital. Our calculation suggests the Mott gap, the same parameter for determining the QSL regime, is tunable with strain. This finding offers a general strategy for manipulating the Mott state in 1T-NbSe2 and related systems via structural distortions, which may be tuned into the potential QSL regime.

20 pages, 5 figures

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• Negative Thermal Expansion Coefficient of Graphene Measured by Raman Spectroscopy
• U(1) Gauge Theory of the Hubbard Model : Spin Liquid States and Possible Application to k-(BEDT-TTF)_2 Cu_2 (CN)_3
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• Direct identification of Mott Hubbard band pattern beyond charge density wave superlattice in monolayer 1T-NbSe2
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Cited by in corpus (9)

• 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)
• Revealing the Charge Density Wave Proximity Effect in Graphene on 1T-TaS${}_2$
• Electronic Density of States of a $U\left(1\right)$ Quantum Spin Liquid with Spinon Fermi Surface. I. Orbital Magnetic Field Effects
• Understanding the flat band in 1T-TaS2 using a rotated basis
• Optical signature for distinguishing between Mott-Hubbard, intermediate and charge-transfer insulators
• Electronic Density of States of a $U\left(1\right)$ Quantum Spin Liquid with Spinon Fermi Surface. II. Zeeman Magnetic Field Effects
• Emergent Quantum Phenomena of Noncentrosymmetric Charge-Density Wave in 1T-Transition Metal Dichalcogenides
• Topical review: the nature of the ground state and possibility of a quantum spin liquid in 1T metal dichalcogenides
• Dynamical control of Coulomb interactions and Hubbard bands in monolayer 1T-TaS${}_2$