### A holographic model of the Kondo effect

**Erdmenger, JK ***(Max-Planck-Institut für Physik, München)*

Friday 20 September 2013, 14:00-14:45

Seminar Room 1, Newton Institute

#### Abstract

Coauthors: C. Hoyos (Tel Aviv Univ.), A. O'Bannon (DAMTP Cambridge), J. Wu (NCTS Taiwan)

We propose a holographic model of the Kondo effect, i.e. of the screening of a magnetic impurity coupled to a bath of conduction electrons at low temperatures. In a (1+1)-dimensional CFT description, this corresponds to an RG flow from an UV to an IR fixed point triggered by a marginally relevant (0+1)-dimensional operator. In the large N limit, with spin SU(N) and charge U(1) symmetries, the Kondo effect appears as a mean-field phase transition in which the U(1) symmetry is spontaneously broken. Inspired by a top-down brane model, we model the Kondo RG flow by an AdS_3 Chern-Simons action coupled to an AdS_2 holographic superconductor. We observe several characteristic features of the Kondo effect in this model, such as dynamical scale generation and a phase shift. Moreover, we find a power-law behaviour of the resistivity with temperature which is consistent with over-screening. Our model may serve as a basis for investigating more involved problems such as Kondo lattices.

#### Presentation

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