Spin gap and L modulated intensity at the low-energy incommensurate magnetic fluctuations in the superconducting state of Sr2RuO4

Low-energy incommensurate (IC) magnetic fluctuations in the multiband superconductor Sr${}_2$RuO${}_4$ is investigated by high-resolution inelastic neutron scattering measurements and random phase approximation (RPA) calculations. Below $T_{\text{c}}$, the substantial spin gap is observed at ${\mathbf{Q}}_{\text{IC}}=(0.3,0.3,L)$ where the quasi-one-dimensional $\alpha$ and $\beta$ sheets consisting of the Fermi surfaces are in good nesting conditions. $L$ modulated intensity of the low-energy IC magnetic fluctuations and our RPA calculations indicate that the superconducting gaps regarding the $\alpha$ and $\beta$ sheets have the horizontal line nodes.