Uemura relation in phase-fluctuation-dominated superconductors

Abstract

Starting from the negative-U Hubbard Hamiltonian of a superconductor with nonretarded interaction on a lattice in three dimensions, we establish an effective theory in terms of the modulus and phase of the superconducting pairing field. This facilitates a scenario where pseudogap is associated with pairing without phase order at T* while superfluidity corresponds to the onset of phase coherence at T c . Building on this framework we calculate from the linear-response theory the penetration depth λ as a function of temperature and interaction strength U. By studying the crossover from the amplitude to the phase-fluctuation-dominated regime, we find a remarkable quasiuniversal behavior in form of the parametric Uemura plot for the superfluid density n s ∼l/λ 2 which we discuss in the context of experiments in underdoped and overdoped high-T c cuprates.