Holographic Kondo and Fano resonances
AbstractWe use holography to study a (1+1)-dimensional conformal field theory (CFT) coupled to an impurity. The CFT is an SU(N) gauge theory at large N, with strong gauge interactions. The impurity is an SU(N) spin. We trigger an impurity renormalization group (RG) flow via a Kondo coupling. The Kondo effect occurs only below the critical temperature of a large-N mean-field transition. We show that at all temperatures T, impurity spectral functions exhibit a Fano resonance, which in the low-T phase is a large-N manifestation of the Kondo resonance. We thus provide an example in which the Kondo resonance survives strong correlations, and uncover a novel mechanism for generating Fano resonances, via RG flows between (0+1)-dimensional fixed points.