Dresden 2017 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
TT: Fachverband Tiefe Temperaturen
TT 39: Superconductivity: (General) Theory
TT 39.7: Talk
Wednesday, March 22, 2017, 11:00–11:15, HSZ 103
Inflated nodes in multiband superconductors with broken time-reversal symmetry — •Carsten Timm1, Daniel F. Agterberg2, and Philip M. R. Brydon3 — 1Institute of Theoretical Physics, Technische Universität Dresden, Germany — 2Department of Physics, University of Wisconsin, Milwaukee, U.S.A. — 3Department of Physics, University of Otago, Dunedin, New Zealand
It is commonly believed that superconductors fall into one of three classes: They can have a full energy gap, a gap with point nodes, or a gap with line nodes. We show that multiband, even-parity, nodal superconducting states that break time-reversal symmetry do not belong to these classes. Instead, they generically possess two-dimensional Fermi surfaces. These Fermi surfaces can be visualized as being generated by “inflating” point and line nodes into spheroids and tori, respectively. The inflated nodes are topologically protected by a Z2 invariant, which we give in terms of a Pfaffian. We also show that such states can be energetically stable in spite of the extended Fermi surfaces; they form the state with the lowest free energy if spin-orbit coupling is sufficiently strong.