Thermal and quantum critical properties of overdoped La2−x SrxCuO4

Abstract

We analyze the extended superfluid density data of Božović et al. taken on homogenous thin films to explore the critical properties of the thermal (TSM) and quantum superconductor to metal (QSM) transitions in overdoped La2 − xSrxCuO4. The temperature dependence reveals remarkable agreement with d-wave BCS behavior, where σ ∝ 1/λ2. No sign of the expected KTB transition is observable. We show that the critical amplitude ρs0 = ρs(T)/(1 − T/Tc) scales as Tc∝ρs01/2 and with that as Tc ∝ ρs(0), empirically verified by Božović et al. Together with additional evidence for BCS behavior in overdoped La2 − xSrxCuO4 we show that the scaling relation Tc∝λ(0)−1∝Δ(0)∝ξ(0)−1∝Hc2(0)−1/2∝λ0−1∝Δ0∝ξ0−1∝Hc20−1/2 applies, by approaching the QSM and TSM transitions. This differs from the dirty limit behavior λ(0) ∝ ξ(0)1/2, maintains the Tc independence of the Ginzburg-Landau parameter κ = λo/ξ0, and puts a stringent constraint on the effect at work. We notice that potential candidates appear to be the nonlocal effects on the penetration depth of clean d-wave superconductors explored by Kosztin and Legget.