Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 18: Superconductivity - Properties, Electronic Structure, Order Parameter II

TT 18.1: Hauptvortrag

Montag, 7. März 2005, 10:00–10:30, TU H2053

Two-Gap Superconductivity in MgB₂ — •Thomas Dahm — Universität Tübingen, Institut für Theoretische Physik

It is by now generally accepted that the recently discovered superconductor MgB₂ is a superconductor with two energy gaps. In this talk we discuss how this happens and address some of its unusual implications. Measurements of the microwave conductivity on MgB₂ thin films have shown an anomalous coherence peak appearing at significantly lower temperatures than in conventional superconductors [1] and the anisotropy ratio of the upper critical field in MgB₂ single crystals shows an unusual strong temperature dependence. We argue that both of these observations are natural consequences of the existence of the two gaps, if the special Fermi surface structure of MgB₂ is taken into account [1,2]. We also examine consequences for the expected intrinsic nonlinear microwave response in MgB₂ [3].

[1] B.B.Jin, T.Dahm et al, Phys. Rev. Lett. 91, 127006 (2003).

[2] T.Dahm and N.Schopohl, Phys. Rev. Lett. 91, 017001 (2003).

[3] T.Dahm and D.J.Scalapino, Appl. Phys. Lett. 85, 4436 (2004).