Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 45: Superconductivity: (General) Theory
TT 45.3: Vortrag
Mittwoch, 13. März 2013, 15:30–15:45, H21
Response and collective modes in two–band superconductors — •Nikolaj Bittner1 and Dietrich Einzel2 — 1Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart, Germany — 2Walther-Meißner-Institut für Tieftemperaturforschung, Bayerische Akademie der Wissenschaften, Walther-Meißner-Straße 8, D-85748 Garching, Germany
We present a systematic study of the response properties of two–band (multi–gap) superconductors with conventional and unconventional spin–singlet pairing correlations. Particular emphasis is on the existence, the dispersion and the general role of a new massive order parameter collective mode, the so–called Leggett mode, which arises as a consequence of interband pairing correlations. The subtle interplay between the gauge mode or Nambu–Goldstone Boson and the Leggett mode is studied in view of both the validity of the charge conservation law and the participation in the Higgs mechanism. The occurrence of the Leggett–mode is analyzed with respect to its experimental observability in all physically relevant spin-independent collisionless response functions like the Lindhard density response, the dielectric function, the supercurrent response (condensate dynamic conductivity) and the electronic Raman response. Possible applications of this theory include systems like various cuprates, MgB2, pnictides and non–centrosymmetric superconductors.