Discovery of a Single-Band Mott Insulator in a van der Waals Flat-Band Compound

Abstract

The Mott insulator provides an excellent foundation for exploring a wide range of strongly correlated physical phenomena, such as high-temperature superconductivity, quantum spin liquid, and colossal magnetoresistance. A Mott insulator with the simplest degree of freedom is an ideal and highly desirable system for studying the fundamental physics of Mottness. In this study, we have unambiguously identified such an anticipated Mott insulator in a van der Waals layered compound Nb3Cl8. In the high-temperature phase, where interlayer coupling is negligible, density functional theory calculations for the monolayer of Nb3Cl8 suggest a half-filled flat band at the Fermi level, whereas angle-resolved photoemission spectroscopy experiments observe a large gap. This observation is perfectly reproduced by dynamical mean-field theory calculations considering strong electron correlations, indicating a correlation-driven Mott insulator state. Since this half-filled band derived from a single 2a1 orbital is isolated from all other bands, the monolayer of Nb3Cl8 is an ideal realization of the celebrated single-band Hubbard model. Upon decreasing the temperature, the bulk system undergoes a phase transition, where structural changes significantly enhance the interlayer coupling. This results in a bonding-antibonding splitting in the Hubbard bands, while the Mott gap remains dominant. Our discovery provides a simple and seminal model system for investigating Mott physics and other emerging correlated states.

arXiv comment23 pages, 4 figures, and the Supplemental Material

References in corpus (27)

• Magic-angle graphene superlattices: a new platform for unconventional superconductivity
• Correlated Insulator Behaviour at Half-Filling in Magic Angle Graphene Superlattices
• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Realization of the field-free Josephson Diode
• Effective Coulomb interaction in transition metals from constrained random-phase approximation
• VO2: A Novel View from Band Theory
• Band insulator to Mott insulator transition in 1T-TaS${}_2$
• General theory of Josephson Diodes
• Observation of topological flat bands in the kagome semiconductor Nb${}_3$Cl${}_8$
• Resolving the VO${}_2$ controversy: Mott mechanism dominates the insulator-to-metal transition
• Electronic structure of optimally doped pnictide Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$: a comprehensive ARPES investigation
• Correlation-driven insulator-metal transition in near-ideal vanadium dioxide films
• Visualizing the atomic scale electronic structure of the Ca2CuO2Cl2 Mott insulator
• Quantum Spin Liquids Unveil the Genuine Mott State
• The insulating phases of vanadium dioxide are Mott-Hubbard insulators
• Screening 2D materials with topological flat bands
• Tunable Magnetic Transition to a Singlet Ground State in a 2D Van der Waals Layered Trimerized Kagomé Magnet
• Relationship between the parent charge transfer gap and maximum transition temperature in cuprates
• Rearrangement of Van-der-Waals Stacking and Formation of a Singlet State at $T=90$ K in a Cluster Magnet
• Competing Coulomb and electron-phonon interactions in NbS${}_2$
• Roles of the Narrow Electronic Band near the Fermi Level in 1T-TaS${}_2$-Related Layered Materials
• Cluster Mott insulators and two Curie-Weiss regimes on an anisotropic Kagome lattice
• Charge density wave instability and pressure-induced superconductivity in bulk 1T-NbS2
• Mottness in two-dimensional van der Waals Nb${}_3$X${}_8$ monolayers (X=Cl, Br, and I)
• Anomalous thickness-dependent electrical conductivity in van der Waals layered transition metal halide, Nb_3Cl_8
• Momentum-Resolved Visualization of Electronic Evolution in Doping a Mott Insulator
• Tunable electronic and magnetic properties of thin Nb${}_3$I${}_8$ nanofilms: interplay between strain and thickness

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• Isolated nearly flat higher Chern band in monolayer transition metal trihalides
• Fingerprints of a charge ice state in the doped Mott insulator Nb${}_3$Cl${}_8$
• Quasi-particle propagation across semiconductor-Mott insulator interfaces
• Evidence of Mott Insulator with Thermally Induced Melting Behavior in Kagome Compound Nb3Cl8
• Antiferromagnetic Spin Fluctuations and Structural Transition in Cluster Mott Insulator Candidate Nb3Cl8 Revealed by 93Nb- and 35Cl-NMR
• From strong to weak correlations in breathing-mode kagome van der Waals materials: Nb${}_3$(F,Cl,Br,I)${}_8$ as a robust and versatile platform for many-body engineering
• Topological Aspects of Dirac Fermions in a Kagomé Lattice
• Emergent dynamical Kondo coherence and competing magnetic order in a correlated kagome flat-band metal CsCr6Sb6
• Dimensionality-Dependent Exciton Dispersion in a Single-Band Mott Insulator
• Robust Orbital-Selective Flat Bands in Transition-Metal Oxychlorides
• Dissipation-Driven Transition of Particles from Dispersive to Flat Bands
• Transmission through multiple Mott insulator - semiconductor wells