Holographic superconductors from gauged supergravity

Abstract

We consider minimal setups arising from different truncations of N = 8 fivedimensional SO(6) gauged supergravity to study phase transitions involving spontaneous breaking of any of the U(1) symmetries in U(1) × U(1) × U(1) ⊂ SO(6). These truncations only keep the three relevant vector fields, four complex scalar fields carrying U(1) charges, plus two neutral scalar fields required by consistency. By considering thermal ensembles with different fixed U(1) charge densities and solving the complete equations including the full back-reaction, in some cases we find instabilities towards the formation of hairy black holes, which lead to second order transitions, resulting from a thermodynamical competition between different sectors. We argue that these should be the dominant thermodynamical instabilities in the full ten-dimensional type IIB theory. In other cases we find unstable branches of hairy black holes that extend to temperatures above a critical temperature ("retrograde condensation"). The results can be used as a first step to understand new aspects of the phase diagram of large N N = 4 SU(N) super Yang-Mills theory with fixed charge densities.