Coherent/incoherent metal transition in a holographic model

Understand

We study AC electric($\sigma$), thermoelectric($\alpha$), and thermal($\bar{\kappa}$) conductivities in a holographic model, which is based on 3+1 dimensional Einstein-Maxwell-scalar action.

• There is momentum relaxation due to massless scalar fields linear to spatial coordinate.
• The model has three field theory parameters: temperature($T$), chemical potential($\mu$), and effective impurity($\beta$).
• At low frequencies, if $\beta < \mu$, all three AC conductivities($\sigma, \alpha, \bar{\kappa}$) exhibit a Drude peak modified by pair creation contribution(coherent metal).