Colloquium in honor of Doug Finnemore by George Crabtree and Brian Maple
| Date/Time: | Monday, 31 Aug 2015 from 4:10 pm to 5:00 pm |
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| Location: | Physics 0003 |
| Phone: | 515-294-5441 |
| Channel: | College of Liberal Arts and Sciences |
| Actions: | Download iCal/vCal | Email Reminder |
"Critical Currents and Vortex Pinning in Model Superconductors" by Dr. George Crabtree. Abstract: Prof Doug Finnemore has contributed extensively to our present understanding of vortex behavior in superconductors. His contributions span an impressively broad range of materials, pinning defects, and geometries. His work is among the first and most thorough to examine the position, motion and pinning force of a single vortex under the influence of temperature and an applied magnetic field using an innovative analysis of the diffraction pattern of critical current vs magnetic field in a Josephson junction. He was a pioneer in developing superconducting microfilament arrays that produced high critical currents simultaneously with high strain tolerance. His work on critical currents in superconducting materials spans the cuprates Bi2Sr2CaCu2O8, YBa2Cu3O7, YBa2Cu4O8, and (LaSr) 2CuO4. His work on the electron-phonon superconductor MgB2 in pure, doped and irradiated forms includes novel synthesis and critical current characterization. Examples from Prof. Finnemore's creative and extensive contributions to the development of vortex physics in superconductors will be highlighted.
"Doug Finnemore's Pioneering Investigations of Superconductivity and Magnetism in Lanthanide and Actinide Materials" by B. Maple. Abstract: Throughout the 1960s and 70s, Professor Doug Finnemore performed a series of pioneering investigations of superconductivity and how it is affected by the presence of localized magnetic moments in lanthanide and actinide elements and alloys. His thorough and precise experiments on La and Th metal established some of the fundamental superconducting properties of these elements and tested several aspects of the BCS theory of conventional superconductivity. In 1958, Matthias, Suhl, and Corenzwit observed that small concentrations of lanthanide (Ln) ions that carry localized magnetic moments (e.g., Gd or Tb) dissolved in La metal strongly suppress its superconducting critical temperature Tc. Following these observations, Finnemore and coworkers performed groundbreaking experiments on the La1-xGdx system that established the phenomenon of gapless superconductivity and on the La0.98Lu0.02-xTbx system that elucidated the effect of spin glass ordering on superconductivity. The observation of gapless superconductivity, in particular, confirmed a prediction of the pair breaking theory of Abrikosov and Gor'kov and attracted an immense amount of interest in the interaction between superconductivity and magnetism, helping to establish this subject as a subfield of condensed matter physics that is still very active on a worldwide scale. Over the years, investigations of the interplay between superconductivity and localized moment magnetism in a wide range of novel materials have uncovered many remarkable phenomena such as reentrant superconductivity due to the Kondo effect or the onset of ferromagnetic order, the formation of a sinusoidally-modulated magnetic state with a wavelength of ~100A that coexists with superconductivity in ferromagnetic superconductors, the coexistence of superconductivity and antiferromagnetic order, and magnetic field induced superconductivity. During the past 3-1/2 decades, four major classes of correlated electron materials have been discovered that exhibit an unconventional type of superconductivity that is frequently found to emerge from a magnetically ordered phase (usually antiferromagnetic, but sometimes ferromagnetic) that is suppressed upon chemical substitution x or application of pressure P. In these materials, the same set of itinerant electrons are involved in both the superconductivity and the magnetism, and the electron pairing appears to be mediated by magnetic excitations. The four major classes of materials and their maximum values of Tc are heavy fermion f-electron materials (Tcmax ~ 2 K), organic conductors (Tcmax ~ 20 K), layered copper oxides (Tcmax ~ 130 K (~165 K at high pressure); HgBa2Ca2Cu3O8), and iron pnictides/chalcogenides (Tcmax ~ 56 K; SmFeAsO1-xFx). Interestingly, magnetism appears to play a central role in the superconductivity of the cuprates and iron-based superconductors, which have the highest confirmed values of Tc observed to date. In this talk, we describe several of Doug Finnemore's groundbreaking experiments and survey some of the striking phenomena produced by the interplay between superconductivity and magnetism that have been discovered during the past half-century.
Biographical Statement - M. Brian Maple: is a Distinguished Professor of Physics and holds the Bernd T. Matthias Endowed Chair at the University of California, San Diego (UCSD). He served as Chair of the Physics Department (2004-2010), Director of the Center for Interface and Materials Science (1990-2010), and Director of the Institute for Pure and Applied Physical Sciences (1995-2009). He leads an active research group in experimental condensed matter physics. The focus of his research is on correlated electron phenomena in novel d- and f-electron materials. Subjects under investigation include high temperature superconductivity, unconventional types of superconductivity, valence fluctuation and heavy fermion behavior, quantum criticality, and exotic types of magnetism. Other research interests include surface science and matter under extreme conditions. Research activities in his laboratory include synthesis of materials in bulk and thin film form, single crystal growth, and transport, thermal, and magnetic measurements as a function of temperature (into the mK range), pressure (up to the Mbar region), and magnetic field (up to 10 tesla). He was ranked among the top 30 scientists for number of citations received for papers published in Physical Sciences between 1990 and 1996 (Science Watch, November/December 1997, published by ISI), and he was identified as one of the world's most Highly Cited Researchers by ISI in 2000.
Professor Maple earned B.S. (physics) and A.B. (mathematics) degrees in 1963 from San Diego State University (SDSU) and M.S. (physics) and Ph.D. (physics) degrees in 1965 and 1969, respectively, from UCSD. His academic appointments have all been in the Physics Department at UCSD: Assistant Research Physicist (1969-1975), Associate Professor (1975-1981), Professor (1981-2005), and Distinguished Professor (2005-present). Professor Maple has held visiting professorships and research positions at the University of Chili, the Instituto de Fisica Jose Balseiro, San Carlos de Bariloche, Argentina, the Institute for Theoretical Physics, University of California, Santa Barbara, Brookhaven National Laboratory, Los Alamos National Laboratory, and the University of Karlsruhe, Germany. He served as Vice-Chairman and Chairman of the Division of Condensed Matter Physics of the American Physical Society (APS) in 1987 and 1988, respectively, and chaired the famous "Woodstock of Physics" Session on High Temperature Superconductivity at the APS March Meeting in New York City in 1987.
Professor Maple is a member of the National Academy of Sciences (2004) and a Fellow of the American Physical Society (1985) and the American Association for the Advancement of Science (1997). He has received numerous awards, including: Excellence in Teaching Award, Revelle College, UCSD (1983), John Simon Guggenheim Fellowship (1984), APS David Adler Lectureship Award (1996), Alexander v. Humboldt Research Award, Germany (1998), Frank H. Spedding Award (1999), APS James C. McGroddy Prize (2000), Bernd T. Matthias Prize (2000), Honorary Professorship, Trzebiatowski Institute for Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw, Poland (2006), and Science Lectureship Award, Chiba University, Tokyo, Japan (2010). He was named Distinguished Alumnus of the Year at UCSD in 1987 and at SDSU, College of Sciences, in 1988.
Professor Maple has lectured on various topics in 13 schools on condensed matter physics and has chaired or co-chaired 14 international conferences. He has been a member of numerous organizing, program and advisory committees for international conferences and workshops. He edited or co-edited 13 volumes of conference proceedings or books on special research topics, and was a member of the editorial boards for 4 physics journals. He has served on numerous review and advisory committees for university physics departments, national and international research institutes and laboratories, and federal funding agencies. From 1986 to 1991, he served on the Scientific and Academic Advisory Committee to the President of the University of California for Livermore and Los Alamos National Laboratories.
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"Critical Currents and Vortex Pinning in Model Superconductors" by G. Crabtree. Abstract is forthcoming.