From an insulating to a superfluid pair-bond liquid

Abstract

We study an exchange coupled system of itinerant electrons and localized fermion pairs resulting in a resonant pairing formation. This system inherently contains resonating fermion pairs on bonds which lead to a superconducting phase provided that long range phase coherence between their constituents can be established. The prerequisite is that the resonating fermion pairs can become itinerant. This is rendered possible through the emergence of two kinds of bond-fermions: individual and composite fermions made of one individual electron attached to a bound pair on a bond. If the strength of the exchange coupling exceeds a certain value, the superconducting ground state undergoes a quantum phase transition into an insulating pair-bond liquid state. The gap of the superfluid phase thereby goes over continuously into a charge gap of the insulator. The change-over from the superconducting to the insulating phase is accompanied by a corresponding qualitative modification of the dispersion of the two kinds of fermionic excitations. Using a bond operator formalism, we derive the phase diagram of such a scenario together with the elementary excitations characterizing the various phases as a function of the exchange coupling and the temperature.

10 pages, 5 figures

References in corpus (11)

• Spin-ladders with spin gaps: A description of a class of cuprates
• The Elusive Bose Metal
• Plaquette Boson-Fermion Model of Cuprates
• Hole and Pair Structures in the t-J model
• True Superconductivity in a 2D "Superconducting-Insulating" System
• Bond operator theory of doped antiferromagnets: from Mott insulators with bond-centered charge order, to superconductors with nodal fermions
• Spin Bose Glass Phase in Bilayer Quantum Hall Systems at $\nu =2$
• Bond operator mean field theory of the half filled Kondo lattice model
• Breakdown of Landau Fermi liquid properties in the $2D$ Boson-Fermion model
• Superconductor-insulator transition driven by local dephasing
• Resonating bipolarons

Cited by in corpus (9)

• Geometric driving of two-level quantum systems
• Critical behaviour in one dimension: unconventional pairing, phase separation, BEC-BCS crossover and magnetic Lifshitz transition
• Boson-Fermion Duality and Metastability in Cuprate Superconductors
• Local dynamical lattice instabilities: Prerequisites for resonant pairing superconductivity
• Spectroscopic Bogoliubov features near the unitary limit
• First Order Superfluid to Bose Metal Transition in Systems with Resonant Pairing
• Temperature-driven BCS-BEC crossover in a coupled boson-fermion system
• Effect of boson on-site repulsion on the superfluidity in the boson-fermion-Hubbard model
• Particle-hole spectral asymmetry at the edge of multiorbital noncentrosymmetric superconductors