The 8th QLC seminar

Speaker：Prof. Ruslan Prozorov (Ames Laboratory and Iowa State University)
Date & Time : Friday, November 29, 2019. 　10:30～12:00
Place : Room 2C5, Kibanto kyoutsu seminar room, Kashiwa campus, The University of Tokyo

Title：Critical Fields of s+- Superconductors

Abstract：

Critical fields of type-II superconductors are among most studied properties linked directly to the characteristic length scales, the London penetration depth and the coherence length. More fundamentally, critical fields are determined by the microscopic pairing mechanism, electronic bandstructure as well as impurity scattering. Unfortunately, ubiquitous comparison of the experiment with so-called “WHH” or similar models is oversimplified and may lead to erroneous conclusions. This is especially important in case of multiband and even more so, s+- superconductors. I will summarize the results of our numerical studies and compare them with the available experiments. For example, I will show that some commonly accepted signatures of multiband superconductivity (e.g., temperature dependent anisotropy) and/or Pauli limiting can often be reproduced in the single-band case when anisotropic Fermi surface and order parameter are considered. This talk is a tribute to Vladimir G. Kogan, my dear colleague and long-time collaborator, the recipient of this year Abrikosov Prize in vortex physics.

• V. G. Kogan and R. Prozorov, “Orbital Upper Critical Field and Its Anisotropy of Clean One- and Two-Band Superconductors.” Rep. Prog. Phys. 75, 114502 (2012).
• V. G. Kogan and R. Prozorov, “Orbital Upper Critical Field of Type-II Superconductors with Pair Breaking.” Phys. Rev. B 88, 24503 (2013).
• V. G. Kogan and R. Prozorov, “Anisotropic Criteria for the Type of Superconductivity.” Phys. Rev. B 90, 54516 (2014).
• V. G. Kogan and R. Prozorov, “Changing the Type of Superconductivity by Magnetic and Potential Scattering.” Phys. Rev. B 90, 180502 (2014).
• V. G. Kogan and R. Prozorov, “Effect of Equatorial Line Nodes on the Upper Critical Field and London Penetration Depth.” Phys. Rev. B 90, 100507 (2014).
• V. G. Kogan and R Prozorov, “Interband Coupling and Nonmagnetic Interband Scattering in s Superconductors.” Phys. Rev. B 93, 224515 (2016).
• V. G. Kogan, R. Prozorov, and A. E. Koshelev, “Temperature-Dependent Anisotropies of Upper Critical Field and London Penetration Depth.” Phys. Rev. B 100, 014518 (2019).

Committee Chair : Takasada SHIBAUCHI (The University of Tokyo)