Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 51: Focus Session: Broken Time Reversal Symmetry in Multiband Superconductors

TT 51.2: Hauptvortrag

Donnerstag, 4. April 2019, 10:00–10:30, H2

Magnetic excitations and their possible role in the superconducting pairing in Sr₂RuO₄ — •Markus Braden¹, Stefan Kunkemöller¹, Kevin Jenni¹, Paul Steffens^1,2, Yvan Sidis³, Zhiqiang Q. Mao⁴, Yoshiteru Maeno⁵, and Igor Mazin⁶ — ¹University of Cologne, Germany — ²Institut Laue Langevin, France — ³Laboratoire Léon Brillouin, France — ⁴Tulane University, USA — ⁵Kyoto University, Japan — ⁶Naval Research Laboratory, USA

The mechanism of the unconventional superconductivity in Sr₂RuO₄ is subject of ongoing debate opposing the impact of antiferromagnetic (AFM) and ferromagnetic (FM) fluctuations. Indirect evidence for FM fluctuations can be deduced from the metallic FM SrRuO₃, while isovalent Ca₂RuO₄ is an AFM Mott insulator [1]. With the recent progress in inelastic neutron scattering, we could follow the AFM signal associated with quasi-one-dimensional bands across the superconducting transition down to very low energies. Even well below twice the superconducting gap, there is no change in the magnetic response in Sr₂RuO₄ [2], which seems incompatible with the picture of a large gap on these Fermi-surface sheets. The quantitative analysis of FM fluctuations in Sr₂RuO₄ was performed with polarized neutron scattering yielding good agreement with reports of specific heat, magnetic susceptibility and NMR. Incorporating this ferromagnetic response into the BCS gap equation, however, does not stabilize a triplet pairing [3].
S. Kunkemöller et al., Phys. Rev. Lett. 115, 247201 (2015)
S. Kunkemöller et al., Phys. Rev. Lett. 118, 147002 (2017)
P. Steffens et al., arXiv1808.05855