Reduction of the Spin Susceptibility in the Superconducting State of Sr2RuO4 Observed by Polarized Neutron Scattering

Recent observations [A. Pustogow et al., Nature (London) 574, 72 (2019).] of a drop of the O-17 nuclear magnetic resonance (NMR) Knight shift in the superconducting state of Sr2RuO4 challenged the popular picture of a chiral odd-parity paired state in this compound. Here we use polarized neutron scattering (PNS) to show that there is a 34 +/- 6% drop in the magnetic susceptibility at the Ru site below the superconducting transition temperature. We measure at lower fields H similar to( )1/3 H-c2 than a previous PNS study allowing the suppression to be observed. The PNS measurements show a smaller susceptibility suppression than NMR measurements performed at similar field and temperature. Our results rule out the chiral odd-parity d = (z) over cap (k(x) +/- ik(y)) state and are consistent with several recent proposals for the order parameter including even-parity B-1g and odd-parity helical states.