Abstrakt
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 [1,2], has been recently overturned [3]. 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 RIGHTWARDS ARROW 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 response of <10% of the normal-state susceptibility, which is sufficient to exclude odd-parity candidates [4]. [1] J. Phys.
Condens. Matter 7, L643 (1995) [2] Nature 396, 658-660(1998) [3] Nature 574, 72-75 (2019) [4] arXiv:2007.13730