, Volume 110, Issue 3-4, pp 873-884

Lateral-Size Effects and Supercurrent Blockade at Mechanical-Controllable Break Junctions of the Heavy-Fermion Superconductors

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Break junctions of the heavy-fermion superconductors CeCu 2 Si 2 , UBe 13 , UPt 3 , URu 2 Si 2 , UPd 2 Al 3 , and UNi 2 Al 3 have been investigated. Josephson-like superconducting anomalies could be found only for low-ohmic contacts, but without the oscillatory Fraunhofer pattern of the critical current in a magnetic field. A systematic study on the contact radius demonstrates that these anomalies are mainly due to Maxwell's resistance being suppressed in the superconducting heavy-fermion phase rather than due to Josephson effect and Andreev reflection. We could not find any superconducting features by vacuum-tunneling spectroscopy.