Non-metallic ground states from holography: features and observables.

I will discuss the features of holographic models in case when the breaking of translations is relevant in the IR and the horizon geometry is not metallic. This can be achieved either via the strong explicit source or via the spontaneous symmetry breaking mechanism.  While in both cases the resulting model is power-law insulating, the features of AC transport are quite different. In case of strong explicit breaking I will also discuss the electric charge density response, which demonstrates "fake plasmon" feature, while the sound mode is absent in the neutral spectrum. Based on 1909.1224, 1812.08132.