Superconducting instability in the Holstein-Hubbard model: A numerical renormalization-group study

C.-H. Pao; H.-B. Schüttler

doi:10.1103/PhysRevB.57.5051

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Superconducting instability in the Holstein-Hubbard model: A numerical renormalization-group study

C.-H. Pao, H.-B. Schüttler

DOI 10.1103/PhysRevB.57.5051 · Physical Review B

T1

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Abstract

We have studied the d-wave pairing instability in the two-dimensional Holstein-Hubbard model at the level of a full fluctuation-exchange approximation which treats both Coulomb and electron-phonon (EP) interaction diagrammatically on an equal footing. A generalized numerical renormalization-group technique has been developed to solve the resulting self-consistent field equations. The d-wave superconducting phase diagram shows an optimal Tc at electron concentration 〈n〉∼0.9 for the purely electronic Hubbard system. The EP interaction suppresses the d-wave Tc which drops to zero when the phonon-mediated on-site attraction Up becomes comparable to the on-site Coulomb repulsion U. The isotope exponent α is negative in this model and small compared to the classical BCS value αBCS=12 or compared to typical observed values in nonoptimally doped cuprate superconductors.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown