Special Colloquium to Honor Vladimir Kogan's 80th Birthday (4 speakers)
|Date/Time:||Monday, 15 Sep 2014 from 4:10 pm to 6:00 pm|
Lev Bulaevskii Los Alamos
James Thompson Oak Ridge
David Farrell Case Western
"MAKING SCANNING SQUID MICROSCOPY QUANTITATIVE" by John Kirtley
Abstract - Scanning SQUID Microscopy (SSM) is a sensitive technique for imaging the magnetic fields above a sample surface. Vladimir Kogan has played a central role in obtaining quantitative values for parameters from SSM measurements. For example, SSM was used to test the interlayer tunneling model for high temperature superconductivity, by imaging the spread of the magnetic fields of vortices trapped between the layers of highly layered superconductors. Vladimir and his co-workers developed a theory for the spreading of the vortex magnetic fields at the surface of a layered superconductor,1 helping to show that the interlayer tunneling mechanism could not supply enough condensation energy to explain the high critical temperatures observed in the cuprate superconductors. Vladimir has also developed the theory for obtaining quantitative values for the penetration depth from SSM measurements of superconductors,2 and for determining the size of the superfluid inhomogeneities in samples with stripes and dots.3 His work has made it possible to obtain quantitative values from the pretty pictures.
1. "Magnetic field of an in-plane vortex outside a layered superconductor", J.R. Kirtley, V.G. Kogan, J.R. Clem, and K.A. Moler, Phys. Rev. B 59, 4343(1999).
2. "Meissner response of anisotropic superconductors", V.G. Kogan, Phys. Rev. B 68, 104511 (2003)
3. "Meissner response of superconductors with inhomogeneous penetration depths", V.G. Kogan and J.R. Kirtley, Phys. Rev. B 83 214521 (2011)
Bio - John Robert Kirtley was awarded his B.S. (1971) and PhD (1976), both in Physics, from the University of California at Santa Barbara. After working as a post-doctoral fellow and research assistant professor at the University of Pennsylvania, he moved to the IBM Thomas J. Watson Research Center as a Research Staff Member (1978). Since taking early retirement from IBM (2006), he has traveled the world, using as a base a position as Senior Research Associate in the Department of Applied Physics at Stanford University. During that time he has been a Medewerker at the University of Twente in Enschede, the Netherlands; a Jubileum Professor at Chalmers University in Gothenberg, Sweden; a Humboldt Senior Fellow in Augsburg, Germany; and held a Chaire d' Excellence of the NanoFondation in Grenoble, France. He is a Fellow of the American Physical Society and the American Association for the Advancement of Physics, and a recipient of the Oliver J. Buckley Prize in Condensed Matter Physics of the APS.
"INTRINSIC JOSEPHSON EFFECT IN LAYERED SUPERCONDUCTORS" by Lev Bulaevskii
Abstract: I will discuss development of theoretical ideas and experimental facts on the vortex matter and plasma resonance in superconductors starting from isotropic ones on the way to layered superconductors with Josephson interlayer coupling. The concepts of anisotropic vortices, Josephson vortices, pancakes, locking transition, combined (crossing) vortex lattice, Josephson resonance and radiation from layered superconductors with Josephson coupling will be considered. Contribution of J. Clem and V. Kogan to this field of Superconductivity is invaluable.
"VORTICES IN SUPERCONDUCTORS: AN EXPERIMENTALIST'S APPRECIATION OF THE WORK OF V.G. KOGAN" by James R. Thompson
Abstract: This talk will give a historical overview of a few important features of superconductors. Of particular interest is the mixed or vortex state, which forms when a superconductor is exposed to a magnetic field large enough to generate vortices - quantized lines of magnetic flux. Two experimental studies will be discussed in which theoretical findings of V. G. Kogan provide an essential framework for interpreting and understanding the results. In one case, the high-Tc superconductor YBa2Cu3Ox was studied  at various oxygen contents x of 6.8-7.0. While removing some oxygen (and charge carriers) hardly changed the superconductive transition temperature Tc, it drastically diminished the material's current-carrying ability. Analysis of the data using theory from Ames gave key insights, as will be described. A second study  examined effects of nonlocal electrodynamics in 'clean' superconductors, which effectively imparts some symmetry of the crystal onto the vortices. Kogan's treatment stimulated experimental investigations of such effects, and his tractable theoretical results enabled a successful description of delicate and subtle features in the studies. A general and accessible discussion of superconductivity is available online at http://superconductors.org .
 J. G. Ossandon et al,, Phys. Rev. B 45, 12534 (1992).
 L. Civale et al., PRL 83, 3920 (1999); K. J. Song et al., PRB 59, R6620 (1999).
Bio: Emeritus Professor of Physics, the University of Tennessee and Distinguished Research and Development Scientist (ret), Oak Ridge National Laboratory. I attended Duke University in Durham, NC where I earned a Ph.D. degree in experimental low temperature physics in 1969. This work was conducted under the direction of Prof. H. Meyer. After active duty in the US Army in Alabama and Vietnam, I joined the Physics faculty at the University of Tennessee. From 1978, I also held an Adjunct appointment in the Materials Science and Technology Division at the Oak Ridge National Laboratory. My research interests center on the magnetic and electrical properties of superconductors and magnetic materials. I am co-owner of 2-3 patents related to this work and a Fellow of the American Physical Society. Awards include one from the US DOE for innovations in superconductivity; a "Nano-50" Award for innovations in enhancing the performance of superconductive materials; and R&D-100 Awards in 2009, 2010 and 2010 for development and characterization of superconducting wire and tapes, and nanoscale magnetic phenomena. I'm now catching up on a backlog of hiking, reading and travel.
"VLADIMIR'S OCTOGESIMA" by David E. Farrell
Abstract: In any talk celebrating somebody's eightieth birthday, it is appropriate to take the long view. Accordingly, I will first review a century of theoretical activity in the area of superconductivity, and draw conclusions regarding the importance of our honoree's work. I will then briefly review the manner in which, for several centuries, distinguished academics have been honored in England's ancient universities. In an attempt to do justice to our honoree's singular character and achievements, I will conclude in the English manner - by delivering an oration in Latin.*
*For those unfamiliar with the language, a translation will be supplied.
Bio: David E. Farrell is from Case Western Reserve University, Physics Dept., 10900 Euclid Avenue Cleveland, Ohio 44106-7079 e-mail: . He was born in Carlisle, England. 1957-60 State Scholar (England), 1960 B.Sc. (First Class, Honors) Imperial College, University of London, 1962 LRAM, Royal Academy of Music, London, 1964 Ph.D., Imperial College, University of London, (Experimental Superconductivity). He was a Research Assistant at the University of London in 1964. 1964-65 Postdoctoral Fellow, Western Reserve University, 1966-67 Instructor Western Reserve University, 1967-72 Assistant Professor, Case Western Reserve University, 1972-81 Associate Professor, Case Western Reserve University, 1981-09 Professor, Case Western Reserve University, 2009- Emeritus Professor, Case Western Reserve University, 1968-69 Consultant, Cleveland Public School System, 1972-75 Consultant, Argonne National Laboratory, 1976-82 Consultant, Gould Inc., (Ocean Systems Division), 1975-76 Exchange Scientist, Institute for Physical Problems, Moscow, 1982-83 Visiting Professor, Oxford University, England, 1996-97 Visiting Professor, Cambridge University, England. Professional Societies include Fellow and the American Physical Society.