Theory of magnetic excitations in the multilayer nickelate superconductor La3Ni2O7

Motivated by the recent reports of high-Tc superconductivity in La₃Ni₂O₇ under pressure, we analyzed theoretically the magnetic excitations in the normal and the superconducting state in this compound, which can be measured by inelastic neutron scattering or resonant inelastic x-ray scattering. We show that the bilayer structure of the spin response allows us to elucidate the role of the interlayer interaction and the nature of the Cooper pairing in a very efficient way. In particular, we demonstrate the key difference between the potential s_±- and d-wave gaps, proposed recently, by comparing the corresponding response in the even and odd channels of the spin susceptibility. We show that the mostly interlayer driven bonding-antibonding s_± Cooper pairing produces a single large spin resonance peak in the odd channel only near the X point, whereas spin resonances in both the odd and the even channel are predicted for the d-wave scenario.