Uemura relation in phase-fluctuation-dominated superconductors

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 lambda 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)similar to1/lambda(2) which we discuss in the context of experiments in underdoped and overdoped high-T-c cuprates.