Strange metals and the AdS/CFT correspondence

TL;DR

This paper reviews the connection between strange metals, quantum impurity models, and the AdS/CFT correspondence, proposing holographic models as mean-field descriptions of strange metal phases in condensed matter physics.

Contribution

It links holographic AdS2 geometries to mean-field theories of strange metals derived from Kondo lattice models, offering a new perspective on their quantum critical behavior.

Findings

Holographic models with AdS2 x R2 geometry relate to mean-field solutions of Kondo lattice models.

Strange metals can be described by a fractionalized Fermi liquid phase.

The AdS/CFT correspondence provides insights into the quantum impurity models and strange metal phases.

Abstract

I begin with a review of quantum impurity models in condensed matter physics, in which a localized spin degree of freedom is coupled to an interacting conformal field theory in d = 2 spatial dimensions. Their properties are similar to those of supersymmetric generalizations which can be solved by the AdS/CFT correspondence; the low energy limit of the latter models is described by a AdS2 geometry. Then I turn to Kondo lattice models, which can be described by a mean- field theory obtained by a mapping to a quantum impurity coupled to a self-consistent environment. Such a theory yields a 'fractionalized Fermi liquid' phase of conduction electrons coupled to a critical spin liquid state, and is an attractive mean-field theory of strange metals. The recent holographic description of strange metals with a AdS2 x R2 geometry is argued to be related to such mean-field solutions of Kondo lattice models.