Topical review: the nature of the ground state and possibility of a quantum spin liquid in 1T metal dichalcogenides

Abstract

The compounds 1T-TaX2 (X = S, Se) and 1T-NbSe2 have been considered as potential hosts of a quantum spin liquid phase. This is based on the widely held view that the Mott-Hubbard mechanism drives the insulating behaviour of its charge density wave ground state, resulting in localized spins, interacting antiferromagnetically, on a geometrically frustrated lattice. However this assumes layer-wise independent behaviour. A growing body of evidence shows not only that inter-layer interactions are very significant in 1T-TaS2, but also that they mediate some of its most interesting functional properties. Here we offer a perspective from the point of view of scanning tunnelling microscopy that helps to visualize the microscopic degrees of freedom of inter-layer interactions in bulk 1T-TaS2, and the associated impact on the local density-of-states, including the occurrence of multiple distinct insulating phases. We consider to what extent the bulk of 1T-TaS2, and its surface terminations can be considered as Mott insulating and whether, or where, quantum spin liquid behaviour might persist. To better understand the bulk behaviour we also draw insights from measurements on isolated monolayers of 1T-TaX2 and 1T-NbSe2, where the confounding complications of inter-layer interactions are absent. We highlight some outstanding questions raised by a comprehensive evaluation of the experimental results, and finally suggest future experiments that could address them.

arXiv comment45 pages, 24 figures. Accepted for publication in Journal of Physics: Condensed Matter

References in corpus (102)

• Anyons in an exactly solved model and beyond
• Quantum Spin Liquids
• Quantum Spin Liquid States
• Ultrafast switching to a stable hidden topologically protected quantum state in an electronic crystal
• Identifying Topological Order by Entanglement Entropy
• Long range Neel order in the triangular Heisenberg model
• Evidence for a spinon Fermi surface in a triangular lattice quantum spin liquid candidate
• Neel order in square and triangular lattice Heisenberg models
• Short-ranged RVB physics, quantum dimer models and Ising gauge theories
• The remarkable underlying ground states of cuprate superconductors
• Is 1T-TaS${}_2$ a 40 year old quantum spin liquid?
• Correlated Insulating States at Fractional Fillings of the WS2/WSe2 Moiré Lattice
• Memristive phase switching in two-dimensional crystals
• Orbital textures and charge density waves in transition metal dichalcogenides
• Spin liquid nature in the Heisenberg $J_1$-$J_2$ triangular antiferromagnet
• Spin liquid phase of the $S=\frac{1}{2}$ $J_1-J_2$ Heisenberg model on the triangular lattice
• A metallic mosaic phase and the origin of Mott insulating state in 1T-TaS2
• Structure and Control of Charge Density Waves in Two-Dimensional 1T-TaS2
• Nanoscale manipulation of the Mott insulating state coupled to charge order in 1T-TaS2
• Visualizing Exotic Orbital Texture in the Single-Layer Mott Insulator 1T-TaSe2
• Competing Spin Liquid States in the Spin-$1/2$ Heisenberg Model On Triangular Lattice
• Valence Bonds in Random Quantum Magnets: Theory and Application to YbMgGaO4
• Momentum-dependent snapshots of a melting charge density wave
• Vanadium dioxide : A Peierls-Mott insulator stable against disorder
• Band insulator to Mott insulator transition in 1T-TaS${}_2$
• A new high-temperature quantum spin liquid with polaron spins
• Three Dimensional Metallic and Two Dimensional Insulating Behavior in Tantalum Dichalcogenides
• Imaging spinon density modulations in a 2D quantum spin liquid
• Mottness versus unit-cell doubling as the driver of the insulating state in 1T-TaS2
• Dirac Spin Liquid on the Spin-1/2 Triangular Heisenberg Antiferromagnet
• Excitation spectra of the spin-1/2 triangular-lattice Heisenberg antiferromagnet
• Metal-insulator Transition in VO2: a DFT+DMFT perspective
• Scaling and data collapse from local moments in frustrated disordered quantum spin systems
• Lifetime of double occupancies in the Fermi-Hubbard model
• Disrupted orbital order and the pseudo-gap in layered 1T-TaS${}_2$
• Ultrafast manipulation of mirror domain walls in a charge density wave
• Ultrafast doublon dynamics in photo-excited 1T-TaS${}_2$
• Collapse of layer dimerization in the photo-induced hidden state of 1T-TaS2
• Zone-center phonons of bulk, few-layer, and monolayer 1T-TaS${}_2$: Detection of the commensurate charge density wave phase through Raman scattering
• Gapless excitations in the ground state of 1T-TaS${}_2$
• The low-temperature highly correlated quantum phase in the charge-density-wave 1T-TaS_2 compound
• Orbital-driven Mottness collapse in 1T-TaS2-xSex transition metal dichalcogenide
• 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
• Coexisting localized and itinerant gapless excitations in a quantum spin liquid candidate 1T-TaS${}_2$
• Ultrafast jamming of electrons into an amorphous entangled state
• Absence of magnetic thermal conductivity in the quantum spin liquid candidate EtMe3Sb[Pd(dmit)2]2 -- revisited
• Correlated electronic states at domain walls of a Mott-charge-density-wave insulator 1T-TaS2
• Spin liquids in geometrically perfect triangular antiferromagnets
• Thermal conductivity of the quantum spin liquid candidate EtMe3Sb[Pd(dmit)2]2: No evidence of mobile gapless excitations
• Diagnosing phases of magnetic insulators via noise magnetometry with spin qubits
• Distinguishing a Mott Insulator from a Trivial Insulator with Atomic Adsorbates
• From Mott Insulator to Band Insulator: A DMFT Study
• Rearrangement of uncorrelated valence bonds evidenced by low-energy spin excitations in YbMgGaO4
• A scanning tunneling microscope for spectroscopic imaging below 90 mK in magnetic fields up to 17.5 T
• Orbital density wave order and electronic correlation driven insulating 1T-TaS2 monolayer
• Ba8CoNb6O24: a spin-1/2 triangular-lattice Heisenberg antiferromagnet in the 2D limit
• Heat transport study of the spin liquid candidate 1T-TaS2
• Quasi one-dimensional metallic band dispersion in the commensurate charge density wave of $1T$-TaS${}_2$
• Evidence for a spinon Kondo effect in cobalt atoms on single-layer 1T-TaSe${}_2$
• Preferential out-of-plane conduction and quasi-one-dimensional electronic states in layered 1T-TaS2
• Photoexcitation Induced Quantum Dynamics of Charge Density Wave and Emergence of a Collective Mode in 1T-TaS${}_2$
• Effect of Stacking Order on the Electronic State of 1T-TaS${}_2$
• Possible strain induced Mott gap collapse in 1T-TaS${}_2$
• Mott versus hybridization gap in the low-temperature phase of $1T$-TaS${}_2$
• Evidence of Dirac Quantum Spin Liquid in YbZn2GaO5
• Mott insulator tuning via structural distortion in monolayer 1T-NbSe2
• Spectral function of the $J_1-J_2$ Heisenberg model on the triangular lattice
• Dynamical Signatures of Symmetry Broken and Liquid Phases in an $S=1/2$ Heisenberg Antiferromagnet on the Triangular Lattice
• Zoology of domain walls in quasi-2D correlated charge density wave of 1T-TaS2
• Multiple crossovers and coherent states in a Mott-Peierls insulator
• Mermin-Wagner physics, (H,T) phase diagram, and candidate quantum spin-liquid phase in the spin-1/2 triangular-lattice antiferromagnet Ba8CoNb6O24
• Stacking order dynamic in the quasi-two-dimensional dichalcogenide 1T-TaS${}_2$ probed with MeV ultrafast electron diffraction
• Magnetic impurity in a $U(1)$-Spin Liquid with a Spinon Fermi-Surface
• Presence and absence of itinerant gapless excitations in the quantum spin liquid candidate EtMe${}_3$Sb[Pd(dmit)${}_2$]${}_2$
• Probing the coupling between a doublon excitation and the charge-density wave in TaS2 by ultrafast optical spectroscopy
• Magnetic Impurity as a Local Probe of the U(1) Quantum Spin Liquid with Spinon Fermi Surface
• Exploring the Charge Density Wave phase of 1$T$-TaSe${}_2$: Mott or Charge-transfer Gap?
• $\text{Ab initio}$ theory of magnetism in two-dimensional $1T$-TaS${}_2$
• Surface structure and stacking of the commensurate $\left(\sqrt{13}\times \sqrt{13}\right)$R13.9° charge density wave phase of 1T-TaS${}_2$(0001)
• Ba8MnNb6O24: a model two-dimensional spin-5/2 triangular lattice antiferromagnet
• ${\mathbb{Z}}_2$ gauge theory for valence bond solids on the kagome lattice
• Fractionalization on the Surface: Is Type-II Terminated $1T$-TaS${}_2$ Surface an Anomalously Realized Spin Liquid?
• Large optical tunability from charge density waves in 1T-TaS${}_2$ under incoherent illumination
• Quantum billiards with correlated electrons confined in triangular transition metal dichalcogenide monolayer nanostructures created by laser quench
• Doublon bottleneck in the ultrafast relaxation dynamics of hot electrons in 1T-TaS_2
• Low-energy behavior of spin-liquid electron spectral functions
• Nonlinear order parameter oscillations and lattice coupling in strongly-driven charge-density-wave systems
• Doublon-like excitations and their phononic coupling in a Mott charge-density-wave system
• Charge density wave surface reconstruction in a van der Waals layered material
• Proposal to detect emergent gauge field and its Meissner effect in spin liquids using NV Centers
• Electronic Density of States of a $U\left(1\right)$ Quantum Spin Liquid with Spinon Fermi Surface. I. Orbital Magnetic Field Effects
• Twisted Bogoliubov quasiparticles in the superconducting NbSe${}_2$ monolayer on graphene
• Electronic Density of States of a $U\left(1\right)$ Quantum Spin Liquid with Spinon Fermi Surface. II. Zeeman Magnetic Field Effects
• Origin of Distinct Insulating Domains in the Layered Charge Density Wave Material 1T-TaS2
• Spectroscopic evidence for possible quantum spin liquid behavior in a two-dimensional Mott insulator
• Identification of soft modes across the commensurate-to-incommensurate charge density wave transition in 1$T$-TaSe${}_2$
• Controlling magnetic frustration in 1T-TaS${}_2$ via Coulomb engineered long-range interactions
• Possible glass-like random singlet magnetic state in 1T-TaS2
• Interlayer Hopping between Surface Mott Insulator and Bulk Band Insulator in layered 1T-TaS_{2}
• Probing complex stacking in a layered material via electron-nuclear quadrupolar coupling
• Behavior under magnetic field of resonance at the edge of the upper Hubbard band in 1T-TaS2