Two-point Functions in a Holographic Kondo Model

Dec 6, 2016
65 pages
Published in:
  • JHEP 03 (2017) 039
  • Published: Mar 7, 2017
e-Print:
Report number:
  • OUTP-16-27P,
  • SISSA-61-2016-FISI,
  • FPAUO-16-16

Citations per year

201620182020202220245132
Abstract: (Springer)
We develop the formalism of holographic renormalization to compute two-point functions in a holographic Kondo model. The model describes a (0 + 1)-dimensional impurity spin of a gauged SU(N ) interacting with a (1 + 1)-dimensional, large-N , strongly-coupled Conformal Field Theory (CFT). We describe the impurity using Abrikosov pseudo-fermions, and define an SU(N )-invariant scalar operator O \mathcal{O} built from a pseudo-fermion and a CFT fermion. At large N the Kondo interaction is of the form OO {\mathcal{O}}^{\dagger}\mathcal{O} , which is marginally relevant, and generates a Renormalization Group (RG) flow at the impurity. A second-order mean-field phase transition occurs in which O \mathcal{O} 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 (1 + 1)-dimensional Anti-de Sitter space. At all temperatures, spectral functions of O \mathcal{O} 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 (0 + 1)-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 −i〈 O \mathcal{O} 2^{2}, which is characteristic of a Kondo resonance.
Note:
  • 65 pages, 17 figures; v2 minor improvements. Version published in JHEP
  • Holography and condensed matter physics (AdS/CMT)
  • AdS-CFT Correspondence
  • Gauge-gravity correspondence
  • field theory: conformal
  • superconductivity: holography
  • renormalization group: flow
  • critical phenomena
  • two-point function
  • Kondo model
  • SU(N)