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RESEARCH PRODUCT

Heavy-fermion superconductivity induced by antiferromagnetic spin fluctuations

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Superconductivity is caused by an attractive interaction between electrons at the Fermi level that induces the pairing of time-reversed electron states to Cooper pairs. Conventionally this attractive interaction is mediated by phonons. Theoretically, non-phonon mediated coupling seems to be likely for heavy-fermion superconductors whose low-temperature dynamics is dominated by antiferromagnetic spin correlations. However, evidence for spin-fluctuation coupling has not yet been experimentally observed. One of the most direct methods of investigation of the superconducting state is tunneling spectroscopy. We prepared cross-type tunneling junctions composed of the heavy-fermion superconductor UPd2Al3 as a base electrode, an AlOx tunneling barrier, and Pb as a counter electrode. The analysis of the differential conductivity of these contacts gives direct evidence for Cooper-pair coupling via the exchange of antiferromagnetic spin fluctuations.