Anomalous superconductivity of Pb/La0.7Sr0.3MnO3 point contacts

Abstract

Recent experimental results indicate the possible realization of an even frequency p-wave triplet superconducting state in proximity affected La0.65Ca0.35MnO3−X(X=Pb,MgB2) point contacts (PCs). Motivated by this we present a study of the current-voltage characteristics and of the dynamic conductance of PCs between Pb and another member of a ferromagnetic manganite family La0.7Sr0.3MnO3 (LSMO). For proximity affected contacts we have observed a spectacular drop of the contact’s resistance with the onset of the Pb superconductivity and, for small voltage, an excess current and doubling of the normal-state conductance. We also detected the subharmonic gap resonances and found that proximity induced superconducting state of LSMO corresponds to that with the energy of the quasiparticle gap much larger than that of Pb. The results most reasonably can be explained by assuming a conversion of spin singlet pairs into triplet pairs at the Pb/LSMO interface and intrinsic superconductivity of LSMO with the actual gap independent on Pb. The mechanism of a conversion has been discussed. Systematic character and repeatability of a number of principal experimental facts suggest that some general physical phenomena have been documented in transport properties of proximity affected singlet superconductor/half-metallic manganite heterostructures.

Source-reported materials — not catalogue approval

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