Semi-holographic models of non-Fermi liquids have been shown to havegenerically stable generalised quasi-particles on the Fermi surface. Althoughthese excitations are broad and exhibit particle-hole asymmetry, they wereargued to be stable from interactions at the Fermi surface. In this work, weuse this observation to compute the density response and collective behaviourin these systems. Compared to the Fermi liquid case, we find that the boundaries of theparticle-hole continuum are blurred by incoherent contributions. However, thereis a region inside this continuum, that we call inner core, within whichsalient features of the Fermi liquid case are preserved. A particularlystriking prediction of our work is that these systems support a plasmoniccollective excitation which is well-defined at large momenta, has anapproximately linear dispersion relation and is located in the low-energy tailof the particle-hole continuum. Furthermore, the dynamic screening potential shows deep attractive regions asa function of the distance at higher frequencies which might lead to long-livedpair formation depending on the behaviour of the pair susceptibility. We alsofind that Friedel oscillations are present in these systems but are highlysuppressed.
展开▼
