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A holographic two-impurity kondo model

A holographic two-impurity kondo model
A holographic two-impurity kondo model
We propose a model of a strongly-interacting two-impurity Kondo system based on the AdS/CFT correspondence, also known as holography. In a Landau Fermi Liquid, the single-impurity Kondo effect is the screening of an impurity spin at low temperature T. The two-impurity Kondo model then describes the competition between the Kondo interaction and the Heisenberg interaction between two impurity spins, also called the RKKY interaction. For spin-1/2 impurities, that competition leads to a quantum phase transition from a Kondo-screened phase to a phase in which the two impurity spins screen one another. Our holographic model is based on a (1+1)-dimensional CFT description of the two-impurity Kondo model, reliable for two impurities with negligible separation in space. We consider only impurity spins in a totally anti-symmetric representation of an SU(N) spin symmetry. We employ a large-N limit, in which both Kondo and RKKY couplings are double-trace, and both Kondo and inter-impurity screening appear as condensation of single-trace operators at the impurities' location. We perform the holographic renormalization of our model, which allows us to identify the Kondo and RKKY couplings as boundary conditions on fields in AdS. We numerically compute the phase diagram of our model in the plane of RKKY coupling versus T, finding evidence for a quantum phase transition from a trivial phase, with neither Kondo nor inter-impurity screening, to a non-trivial phase, with both Kondo and anti-ferromagnetic inter-impurity screening. More generally we show, just using SU(N) representation theory, that ferromagnetic correlations must be absent at leading order in the large-N limit. Our holographic model may be useful for studying many open problems involving strongly-interacting quantum impurities, including for example the Kondo lattice, relevant for describing the heavy fermion compounds.
1029-8479
O'bannon, Andrew
f0c14b6c-5b74-4319-8432-f9eba1e20cf3
Probst, Jonas
79a41e05-0c37-4efd-844d-cda7815aa622
Papadimitriou, Ioannis
61aeb3c8-7ab7-44db-a3ee-846392b997ba
O'bannon, Andrew
f0c14b6c-5b74-4319-8432-f9eba1e20cf3
Probst, Jonas
79a41e05-0c37-4efd-844d-cda7815aa622
Papadimitriou, Ioannis
61aeb3c8-7ab7-44db-a3ee-846392b997ba

O'bannon, Andrew, Probst, Jonas and Papadimitriou, Ioannis (2016) A holographic two-impurity kondo model. Journal of High Energy Physics, 2016 (103), [103]. (doi:10.1007/JHEP01(2016)103).

Record type: Article

Abstract

We propose a model of a strongly-interacting two-impurity Kondo system based on the AdS/CFT correspondence, also known as holography. In a Landau Fermi Liquid, the single-impurity Kondo effect is the screening of an impurity spin at low temperature T. The two-impurity Kondo model then describes the competition between the Kondo interaction and the Heisenberg interaction between two impurity spins, also called the RKKY interaction. For spin-1/2 impurities, that competition leads to a quantum phase transition from a Kondo-screened phase to a phase in which the two impurity spins screen one another. Our holographic model is based on a (1+1)-dimensional CFT description of the two-impurity Kondo model, reliable for two impurities with negligible separation in space. We consider only impurity spins in a totally anti-symmetric representation of an SU(N) spin symmetry. We employ a large-N limit, in which both Kondo and RKKY couplings are double-trace, and both Kondo and inter-impurity screening appear as condensation of single-trace operators at the impurities' location. We perform the holographic renormalization of our model, which allows us to identify the Kondo and RKKY couplings as boundary conditions on fields in AdS. We numerically compute the phase diagram of our model in the plane of RKKY coupling versus T, finding evidence for a quantum phase transition from a trivial phase, with neither Kondo nor inter-impurity screening, to a non-trivial phase, with both Kondo and anti-ferromagnetic inter-impurity screening. More generally we show, just using SU(N) representation theory, that ferromagnetic correlations must be absent at leading order in the large-N limit. Our holographic model may be useful for studying many open problems involving strongly-interacting quantum impurities, including for example the Kondo lattice, relevant for describing the heavy fermion compounds.

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Accepted/In Press date: 31 December 2015
Published date: 18 January 2016
Organisations: Theory Group

Identifiers

Local EPrints ID: 411630
URI: http://eprints.soton.ac.uk/id/eprint/411630
ISSN: 1029-8479
PURE UUID: 9f941a93-622f-42b8-b817-64ec3d5fe7e1
ORCID for Andrew O'bannon: ORCID iD orcid.org/0000-0001-7862-783X

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Date deposited: 21 Jun 2017 16:31
Last modified: 22 Nov 2021 03:09

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Contributors

Author: Andrew O'bannon ORCID iD
Author: Jonas Probst
Author: Ioannis Papadimitriou

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