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A. Pustogow, A. Chronister, S. Brown:
"Evidence for even parity unconventional superconductivity in Sr2RuO4";
Vortrag: APS March Meeting 2021, online; 15.03.2021 - 19.03.2021.

The physical picture of unconventional superconductivity (SC) in Sr2RuO4, which was considered a solid-state analogue to the superfluid 3He-A phase for more than two decades, has been recently overturned. Here we use 17O NMR spectroscopy to probe the nature of the SC state in Sr2RuO4 and its evolution with magnetic field. The drop of Knight shift K is measured in the limit T → 0 across the field-tuned transition down to B/Bc2 < 0.2. While K includes contributions of both field-induced quasiparticles (QP) and a possible spin polarization of the condensate (of order unity for a p-wave state), the specific heat C/T includes only the QP term. By comparing the field dependence of K and C/T, we establish an upper bound for the condensate magnetic response of < 10% of the normal-state susceptibility, which is sufficient to exclude odd-parity candidates.