Magnetic-field penetration depth in TI2Ba2CuO6+δ in the overdoped regime

THE magnetic field penetration depth λ is a basic parameter of superconductivity, related to ns/m* (superconducting carrier density/effective mass) as λ-2 ∝ ns/m* in the limit where the coherence length ζ is much shorter than the mean free path l (the 'clean limit'). Muon spin relaxation (µSR) measurements1,2 of λ in high-transition-temperature (high-Tc ) copper oxide superconductors have revealed remarkable correlations between Tc and ns/m*: …