© David Pines.
The spin-fluctuation induced interaction between quasiparticles operates in much the same way as their phonon-interaction, with spin replacing charge. Thus a quasiparticle with spin s can induce a spin-fluctuation of momentum q, which is in turn picked up by a second quasiparticle of spin s'. Unlike the charged case, the resulting induced interaction can be highly momentum dependent, reflecting as it does any momentum dependence of the background material spin fluctuations. (Unit: 8)