Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 30: Superconductivity - Poster Session

TT 30.11: Poster

Monday, March 31, 2014, 15:00–19:00, P2

Strong coupling behavior of the neutron resonance mode in unconventional superconductors — •Patrik Hlobil, Boris Narozhny, and Jörg Schmalian — Karlsruhe Institute of Technology

We analyze whether and how the neutron resonance mode in unconventional superconductors is affected by higher order corrections in the coupling between spin excitations and fermionic quasiparticles and find that in general such corrections cannot be ignored. In particular, we find that in two spatial dimensions(d=2) the corrections are of same order as the leading, weak coupling contributions demonstrating that the neutron resonance mode in unconventional superconductors is a strong coupling phenomenon. The origin of this behavior lies in the quantum-critical nature of the low energy spin dynamics in the superconducting state and the feedback of the resonance mode onto the fermionic excitations. While quantum critical fluctuations occur in any dimensionality d<3, they can be analyzed in a controlled fashion by means of the epsilon-expansion (epsilon=3-d), such that the leading corrections to the resonance mode position are small. Even if higher order corrections are taken into account, the resonance mode emerges only if the phase of the superconducting gap function varies on the Fermi surface, making it a powerful tool to investigate the microscopic structure of the pair condensate.