Insulator-metal transition on the triangular lattice

Abstract

Mott insulators with a half-filled band of electrons on the triangular lattice have been recently studied in a variety of organic compounds. All of these compounds undergo transitions to metallic/superconducting states under moderate hydrostatic pressure. We describe the Mott insulator using its hypothetical proximity to a Z_2 spin liquid of bosonic spinons. This spin liquid has quantum phase transitions to descendant confining states with Neel or valence bond solid order, and the insulator can be on either side of one of these transitions. We present a theory of fermionic charged excitations in these states, and describe the route to metallic states with Fermi surfaces. We argue that an excitonic condensate can form near this insulator-metal transition, due to the formation of charge neutral pairs of charge +e and charge -e fermions. This condensate breaks the lattice space group symmetry, and we propose its onset as an explanation of a low temperature anomaly in kappa-(ET)2Cu2(CN)3. We also describe the separate BCS instability of the metallic states to the pairing of like-charge fermions and the onset of superconductivity.

26+15 pages

References in corpus (21)

• Spin Liquid State in an Organic Mott Insulator with Triangular Lattice
• Quantum Orders and Symmetric Spin Liquids
• Weak magnetism and non-Fermi liquids near heavy-fermion critical points
• Fractionalized Fermi liquids
• Variational study of triangular lattice spin-1/2 model with ring exchanges and spin liquid state in κ-(ET)_2 Cu_2 (CN)_3
• Ising models of quantum frustration
• Short-ranged RVB physics, quantum dimer models and Ising gauge theories
• Spin Liquid States on the Triangular and Kagome Lattices: A Projective Symmetry Group Analysis of Schwinger Boson States
• Spin-Liquid phase of the Multiple-Spin Exchange Hamiltonian on the Triangular Lattice
• Overscreened multi-channel SU(N) Kondo model : large-N solution and Conformal Field Theory
• Strong electronic correlations in superconducting organic charge transfer salts
• Amperean Pairing Instability in the U(1) Spin Liquid State with Fermi Surface and Application to $\kappa -(BEDT-TTF{)}_{2}C{u}_2(CN{)}_3$
• The Hubbard model on the triangular lattice: Spiral order and spin liquid
• Emergence of inhomogeneous moments from spin liquid in the triangular-lattice Mott insulator $\kappa$-(ET)${}_2$Cu${}_2$(CN)${}_3$
• Universal Magnetic Properties of Frustrated Quantum Antiferromagnets in Two Dimensions
• Algebraic charge liquids
• SU(2) gauge theory of the Hubbard model and application to the honeycomb lattice
• Mott Transition in a Valence Bond Solid Insulator with a Triangular Lattice
• Depletion of the Bose-Einstein condensate in Bose-Fermi mixtures
• Hole dynamics in an antiferromagnet across a deconfined quantum critical point
• Sum Rules and Ward Identities in the Kondo Lattice

Cited by in corpus (20)

• Continuous Mott transition in semiconductor moiré superlattices
• Quantum frustration in organic Mott insulators: from spin liquids to unconventional superconductors
• Theory of a continuous Mott transition in two dimensions
• Lattice effects and entropy release at the low-temperature phase transition in the spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Global phase diagrams of frustrated quantum antiferromagnets in two dimensions: doubled Chern-Simons theory
• The Paired Electron Crystal: order from frustration in the quarter-filled band
• Pressure-Tuned Exchange Coupling of a Quantum Spin Liquid in the Molecular Triangular Lattice $\kappa$-(ET)${}_2$Ag${}_2$(CN)${}_3$
• Dynamics and transport of the Z_2 spin liquid: application to kappa-(ET)2Cu2(CN)3
• Anisotropic charge dynamics in the quantum spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Critical Spin Liquid versus Valence Bond Glass in Triangular Lattice Organic $\kappa$-(ET)${}_2$Cu${}_2$(CN)${}_3$
• Molecular Quantum Materials: Electronic Phases and Charge Dynamics in Two-Dimensional Organic Solids
• Destruction of Neel order in the cuprates by electron-doping
• Mott Transition and Superconductivity in Quantum Spin Liquid Candidate NaYbSe${}_2$
• Paired electron pockets in the hole-doped cuprates
• Microscopic phase separation in triangular-lattice quantum spin magnet kappa-(BEDT-TTF)2Cu2(CN)3 probed by muon spin relaxation
• Gapless spin liquid and pair density wave of the Hubbard model on three-leg triangular cylinders
• Dynamical reduction of the dimensionality of exchange interactions and the "spin-liquid" phase of $\kappa$-(BEDT-TTF)${}_{2}X$
• Impurities in triangular lattice spin 1/2 antiferromagnet
• Charge disproportionation in the spin-liquid candidate $\kappa$-(ET)${}_2$Cu${}_2$(CN)${}_3$ at 6 K revealed by ${}^{63}$Cu NQR measurements
• Low-temperature lattice effects in the spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$