Objectives and Relevance to Program Objectives: This recommended award would support a three-year cooperative research project between Professor Gregory R. Stewart, University of Florida, and Professor Frank Steglich, Technische Hochschule, Darmstadt, Federal Republic of Germany. They will try to characterize new heavy fermion systems and those that are already known by using resistivity, magnetic susceptibility, specific heat in fields to 25T, thermal expansion, and thermopower at temperatures down to 0.050K. This proposal deals with a topic of high current interest in solid state physics, superconductivity in highly- correlated-electron metals with an effective electron mass of 200 me. Professor Steglich has found that high-mass electrons (heavy fermions) are the superconducting components of certain materials. The reason why some systems become superconducting below 1K, while others become magnetic or do not order at all remains unexplained. The proposed cooperative research will address this issue, as well as other questions concerning the cause of the heavy fermion ground state and whether superconductivity will be observed in heavy fermion systems due to standard superconductivity electron pairing. The research will benefit from the experience of the two researchers in working together and from the equipment available in their two laboratories. The project thus contributes to an important objective of NSF's cooperative science programs with Western Europe, which is to stimulate scientific progress by bringing together scientists from the U.S. and Europe who have similar research interests and who wish to engage in mutually beneficial research cooperation. Funds from this award would support necessary transportation and partial subsistence expenses for the U.S. principal investigator. Return visits by Professor Steglich are anticipated. Merit of Proposal: The cooperating U.S. and foreign investigators are respected for their previous research accomplishments, and there is a very good prospect that this proposed research will lead to a significant contribution to scientific knowledge. The proposed cooperation presents the U.S. investigator with the opportunity to work with a leading foreign research group and to use highly specialized facilities abroad that are complementary to his own. The work plan is sound and the budget is reasonable. Research in this field is currently being vigorously pursued in the U.S. and abroad. The Deutsche Forschungsgemeinschaft (DFG) is providing German counterpart support for the project and has approved the inclusion of this activity under the Memorandum of Understanding between the NSF and the DFG. Funding: This award will not duplicate other funding. The German Academic Exchange Service (DAAD) will support the travel and one-month of per diem for Professor Stewart during the first year of this award.
