US-Federal Republic of Germany Cooperative Research on HeavyFermion Systems

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This award supports Professor Gregory R. Stewart of the University of Florida to collaborate in research on the physics of heavy fermion systems with Professor Frank Steglich of the Institute for Nuclear Physics of the Technical University of Darmstadt, Federal Republic of Germany. The collaborating laboratories bring substantially complementary experimental expertise to the proposed study of >superconductivity in fermions. Professor Steglich's group discovered the first heavy fermion >superconductor. They have considerable expertise and collective knowledge in specific heat, critical fields, thermal expansion, and thermopower and in working with very low temperatures (0.050 Kelvin.) The University of Florida group offers substantial strengths in Uranium.Beryllium13 (UBe.13) sample preparation and studies of small mass.specific heat in high magnetic fields. Heavy fermion systems display anomalously large specific heats at low temperatures which, when coupled with their nearness to magnetic behavior, makes the occurrence of superconductivity in these Cesium and Uranium based compounds unexpected. The collaborating research groups will study the nature of the superconducting pairing and the relationship between normal state properties and superconductivity. They will build on their recent breakthrough in understanding the source of the normal state high effective mass in UBe.13, in order to explore possible implications for superconductivity. Advances in understanding heavy fermion electron systems may have long term applications in magnetism and superconductivity based on their unusual properties and their similarities in some respects to high temperature superconductors.