Holographic superconductors from Einstein-Maxwell-Dilaton gravity

We construct holographic superconductors from Einstein-Maxwell-dilaton gravity in 3+1 dimensions with two adjustable couplings α and the charge q carried by the scalar field. For the values of α and q we consider, there is always a critical temperature at which a second order phase transition occurs between a hairy black hole and the AdS RN black hole in the canonical ensemble, which can be identified with the superconducting phase transition of the dual field theory. We calculate the electric conductivity of the dual superconductor and find that for the values of α and q where α/q is small the dual superconductor has similar properties to the minimal model, while for the values of α and q where α/q is large enough, the electric conductivity of the dual superconductor exhibits novel properties at low frequencies where it shows a “Drude Peak” in the real part of the conductivity.