Magnetic penetration depth in single-crystal YBa2Cu3O7-δ

We report the first measurement of the magnetic penetration depth λ(T, θ) in single crystals of YBa2Cu3O7-δ (δ∼0.1). Results are consistent with conventional s-wave pairing, and yield penetration depths of λab(0)=1415±30 Å and λc(0)>7000 Å, parallel and perpendicular to the basal plane, respectively. Comparative data on sintered YBa2Cu3O7 are also shown to be consistent with the single-crystal results. The muon-spin-rotation data, together with specific-heat results, indicate a two-dimensional carrier density of η2D≈8×1014 carriers cm-2 and a basal-plane effective mass of mab*me≈10.