Bernoulli potentials in superconductors- how electric fields help to understand superconductors
speaker: Klaus Morawetz (Chemnitz University of Technology)abstract: Electrostatic potentials have been measured at surfaces of superconductors in order to access directly the gap and material parameters 1,2. The reason why no thermodynamic corrections are measured as predicted by the theory, e.g. by Rickayzen, has remained a puzzle for almost 30 years 3. We found the solution in the Budd-Vannimenus theorem and could show that the homogeneous surface potential becomes indeed independent of the pairing mechanism due to the surface dipoles 4. To access thermodynamic corrections one has to look deeper in the bulk like in an experiment by Kumagai et al. 5. From the quadrupole shift of the NMR spectra they deduced an electric charge of the vortex core in YBCO and found a very large magnitude and an unexpected sign. We show that the charge transfer between Cu chains and planes reverses the sign of the quadrupole shift and enhances its magnitude 6. To this end we develop the theory of electrostatic potentials above the Abrikosov vortex lattice within Bardeen's extension of the Ginzburg-Landau theory to low temperatures 7,8. Unlike previous studies we include the surface dipole 9 and propose that the inhomogeneous electrostatic potentials can yield informations about material parameters 10. As a first application the deformation of the crystal due to the presence of vortices is calculated and the corresponding effective mass of vortices is suggested to be measured 11]. The experimentally confirmed Bernoulli potential is a consequence of the correlated density which follows from the concept of nonlocal kinetic theory 12,13. Therefore we see this Bernoulli potential as a justification of our kinetic equation of nonlocal and non-instantaneous character which has unified the achievements of transport in dense gases with the quantum transport of dense Fermi systems. 1 J. Bok, J. Klein, Phys. Rev. Lett. 20, 660 (1968). 2 T. D. Morris, J. B. Brown, Physica 55, 760 (1971). 3 G. Rickayzen, J. Phys. C 2, 1334 (1969). 4 P. Lipavsky, J. Kolacek, J. J. Mares, K. Morawetz, Phys. Rev. B 65, 012507 (2001). 5 K. Kumagai, K. Nozaki, Y. Matsuda, Phys. Rev. B 63, 144502 (2001). 6 P. Lipavsky, J. Kolacek, K. Morawetz, E. H. Brandt, Phys. Rev. B 66, 134525 (2002). 7 P. Lipavsky, J. Kolacek, K. Morawetz, E. H. Brandt, Phys. Rev. B 65, 144511 (2002). 8 P. Lipavsky, et al., Phys. Rev. B 69, 024524 (2004). 9 P. Lipavsky, et al., Phys. Rev. B 70, 104518 (2004). 10 P. Lipavsky, et al., Phys. Rev. B 71, 024526 (2005). 11 P. Lipavsky, K. Morawetz, J. Kolacek, E. H. Brandt, Phys. Rev. Lett. (2006). Sub. cond-mat0609669. 12 P. Lipavsky, K. Morawetz, V. Spicka, Kinetic equation for strongly interacting dense Fermi systems, vol. 26,1 of Annales de Physique (EDP Sciences, Paris, 2001). 13 K. Morawetz, P. Lipavsky, V. Spicka, Ann. of Phys. 294, 134 (2001).
timetable:
Thu 12 Jul, 18:30 - 18:55, Aula Dini
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