Testardi correlation, flux quantization, and Josephson effect
* SPEAKERS
Name
Affiliation
E-mail
Yong-Jihn Kim
University of Puerto Rico
* HOST(Applicant)
Name
Affiliation
E-mail
-
* DATE / TIME
2005-06-08, 3:00 p.m.
* PLACE
Seminar Room #512, APCTP Headquarters
* ABSTRACT
This talk is about the recent works on superconductivity by me and my collaborators. First, we discuss Testardi뭩 empirical universal correlation of Tc and the resistance ratio, which is due to the decoupling of electrons and phonons by weak localization. In fact, the Testardi correlation has provided definitive proof of phonon mechanism in MgB2, whereas other techniques were not conclusive. Second, we talk about our new interpretation of flux quantization in superconducting cylinders in the presence of Aharonov뺹ohm flux. We have found that flux quantization is due to the flux dependence of the pairing interaction, whereas Byers and Yang attributed flux quantization to the flux-dependence of kinetic energies of the Cooper pairs, which does not agree with the observation of persistent current in normal metal rings at low temperature. Finally, we describe the Cooper pair wavefunction approach to the Josephson effects. It is shown that the Josephson tunneling is limited by the size of the Cooper pair and its shrinking during the tunneling, leading to the threshold resistance, which is in agreement with observations in SIS junctions of low Tc superconductors, such as Sn, Pb, and Nb. This understanding also explains why the big gap of MgB2 does not show the supercurrents, unlike the small gap
