Fig. 2: Feynman diagrams for perturbative calculations.

a Dyson equation for the magnon Green’s function. The thin and the thick wavy lines are the bare and the renormalized magnon Green’s functions, respectively. The shaded circle represents the magnon self-energy Π. b The fully renormalized charge polarization bubble. Thick straight lines are the fermion propagators and shaded circle represents the vertex function in the fermion-boson model Eq. (5). c–g Feynman diagrams for the charge polarization bubble. At leading order in interfacial exchange coupling \(\tilde{J}\), there are (c, d) the self-energy diagrams and (e) the vertex diagrams. On the next leading order, the potentially relevant diagrams are (f, g) the Aslamazov-Larkin diagrams.