Nearly Insulating Strongly Correlated Systems: Gossamer Superconductors and Metals

TL;DR

This paper introduces the Gossamer Hamiltonian, a novel model capturing strong electronic correlations in superconductors and metals, explaining their transition to insulating states and the persistence of superconductivity despite strong repulsion.

Contribution

It presents a new Gossamer Hamiltonian with an exact ground state, incorporating attractive interactions and describing strongly correlated superconductors and metals.

Findings

Gossamer Hamiltonian has an exact ground state.

Superconducting gap remains despite strong repulsion.

Metallic and superconducting states transition to insulators with increased Coulomb repulsion.

Abstract

Recently a new phenomenological Hamiltonian was proposed to describe the superconducting cuprates in which correlations and on-site Coulomb repulsion are introduced by partial Gutzwiller projection. This Gossamer Hamiltonian has an exact ground state and differs from the t-J and Hubbard Hamiltonians in possessing a powerful attractive interaction among electrons responsible for Cooper pairing in the d-wave channel. It is a faithful description for a superconductor with strong on-site electronic repulsion. The superconducting tunneling gap remains intact and despite on-site repulsion. Near half-filling the Gossamer superconductor with strong repulsion has suppressed photoemission intensities and superfluid density, is unstable toward an antiferromagnetic insulator and possesses an incipient Mott-Hubbard gap. The Gossamer technique can be applied to metallic ground states thus possibly serving as an apt description of strongly correlated metals. Such a Gossamer metallic phase, just as the Gossamer superconducting one, becomes arbitrarily hard to differentiate from an insulator as one turns the Coulomb correlations up near half-filling. Both the metallic and superconducting states undergo a quantum phase transition to an antiferromagnetic insulator as one increases the on-site Coulomb repulsion. In the Gossamer model we reach the critical point at half-filling by fully projecting out the double occupancy. Such a critical point might be the Anderson Resonating Valence bond state.