ETD

• collective modes
• condensed matter
• linear response
• plasmons
• quantum geometry
• quantum metric
• topology

The real part of the quantum geometric tensor, the quantum metric, has been shown to be related to various physical quantities, such as the superfluid stiffness of flat-band superconductors and the electron-electron interactions leading to Kohn-Luttinger superconductivity. It is therefore interesting to study its effects on the collective density modes of interacting fermions, known as plasmons.
We study plasmons in a model in which a single dimensionless parameter tunes the quantum metric while leaving the band energies untouched and the Berry curvature identically zero. We first compute the non-interacting density response function of the model, both on the real and imaginary frequency axis. From it we build the dielectric function within the random phase approximation and extract the information about the collective modes, studying how the metric impacts their dispersion and spectral weight.