Reanalysis of the magnetic field dependence of the penetration depth: Observation of the nonlinear Meissner effect - art. no. 180405

We examine recent high-precision experimental data on the magnetic field, H , dependence of the penetration depth lambda (H) in YBa2Cu3O7-delta for sev eral field directions in the a-b plane. In a theoretical analysis that inco rporates the effects of orthorhombic symmetry, we show that the data at suf ficiently high magnetic fields and low temperatures are in quantitative agr eement with the theoretical predictions of the nonlinear Meissner effect.