Normal and anomalous responses of the Fermi-liquid in the charge and spin channels

By means of the perturbative diagram approach the effects of vertex corrections on the charge and spin responses of the Fermi liquid are considered. It is shown that the interaction in the particle-hole channel induces the multipair excitations in both the charge and spin channels. Such excitations lead to the appearance of the anomalous Fermi liquid term Imχ ∼ -ω/T in the charge and spin responses of the Fermi liquid in addition to the normal response ∼ -ω/vFk. Such a contribution of the anomalous term to the charge and spin responses is in agreement with the marginal Fermi-liquid hypothesis proposed by Varma et al. to explain the universal anomalies in the normal state of the cuprate high-Tc superconductors