Superfluid density in cuprate high-T(c)superconductors: A new paradigm

We show that the Uemura relation, namely T-c proportional to superfluid density rho(s), is not generally satisfied in high-T-c superconductors. Instead, a modified plot of T-c/Delta(0) versus rho(s) where Delta(0) is the maximum d-wave gap at T=0, exhibits universal features that point to an alternative interpretation of the underlying physics. In the underdoped region this plot exhibits the canonical negative curvature expected when a ground-state correlation competes with superconductivity (SC) by opening up a gap (the pseudogap) in the normal-state density of states. Moreover we observe simple linear relations between T(c)rho(s), the electronic entropy at T-c, and the critical impurity concentration for suppressing SC. These relations confirm that the pseudogap persists to T=0, strongly modifying the SC ground state.