Universal correlations between Tc and ns/m (carrier density over effective mass) in high-Tc cuprate superconductors.

Abstract

The muon-spin-relaxation rate sigma has been measured in sixteen specimens of high-T/sub c/ cuprate superconductors (the 2:1:4, 1:2:3, 2:2:1:2, and 2:2:2:3 series). This has allowed us to study the magnetic field penetration depth lambda and thus the superconducting carrier density n/sub s/ divided by the effective mass m/sup */ (sigmaproportional1/lambda/sup 2/proportionaln/sub s//m/sup */). A universal linear relation between T/sub c/ and sigma(T..-->..0)proportionaln/sub s//m/sup */ has been found with increasing carrier doping. In heavily doped samples, however, T/sub c/ shows saturation and suppression with increasing n/sub s//m/sup */. This saturation starts at different values of n/sub s//m/sup */ for materials with different multiplicities of CuO planes.