12 research outputs found
Two-point functions in a holographic Kondo model
We develop the formalism of holographic renormalization to compute two-point
functions in a holographic Kondo model. The model describes a
-dimensional impurity spin of a gauged interacting with a
-dimensional, large-, strongly-coupled Conformal Field Theory (CFT).
We describe the impurity using Abrikosov pseudo-fermions, and define an
-invariant scalar operator \mathcalO built from a pseudo-fermion and
a CFT fermion. At large the Kondo interaction is of the form
\mathcalO^\dagger \mathcalO, which is marginally relevant, and
generates a Renormalization Group (RG) flow at the impurity. A second-order
mean-field phase transition occurs in which \mathcalO condenses below a
critical temperature, leading to the Kondo effect, including screening of the
impurity. Via holography, the phase transition is dual to holographic
superconductivity in -dimensional Anti-de Sitter space. At all
temperatures, spectral functions of \mathcalO exhibit a Fano resonance,
characteristic of a continuum of states interacting with an isolated resonance.
In contrast to Fano resonances observed for example in quantum dots, our
continuum and resonance arise from a -dimensional UV fixed point and RG
flow, respectively. In the low-temperature phase, the resonance comes from a
pole in the Green's function of the form , which
is characteristic of a Kondo resonance