Evidence for nonmonotonic magnetic field penetration in a type-I superconductor

The ability of the polarized neutron reflectivity (PNR) technique to reveal the non-local electrodynamics effect in the profile of magnetic field penetrated into a superconductor in the Meissner state is explored with an extreme low-¿ type-I superconductor. The sample is a thick film of pure indium deposited on a silicon oxide substrate having a neutron refraction index smaller than that for indium. It is shown that the PNR technique allows one to distinguish between exponential and non-exponential shape of the field profile. The data obtained are consistent with the magnetic field distribution following from the non-local theory