Emergent quantum criticality, Fermi surfaces, and AdS2

TL;DR

This paper explores how gravity solutions with AdS_2 regions relate to emergent quantum criticality and Fermi surfaces in dual field theories, providing analytic insights into low-energy excitations and spectral functions.

Contribution

It offers a new analytic understanding of holographic Fermi surfaces and their low-energy behavior through the lens of emergent IR conformal field theories.

Findings

Scaling behavior near Fermi surfaces is governed by IR conformal dimensions.

Spectral functions can be exactly of the Marginal Fermi Liquid form.

Provides a holographic framework for understanding quantum criticality.

Abstract

Gravity solutions dual to d-dimensional field theories at finite charge density have a near-horizon region which is AdS_2 x R^{d-1}. The scale invariance of the AdS_2 region implies that at low energies the dual field theory exhibits emergent quantum critical behavior controlled by a (0+1)-dimensional CFT. This interpretation sheds light on recently-discovered holographic descriptions of Fermi surfaces, allowing an analytic understanding of their low-energy excitations. For example, the scaling behavior near the Fermi surfaces is determined by conformal dimensions in the emergent IR CFT. In particular, when the operator is marginal in the IR CFT, the corresponding spectral function is precisely of the "Marginal Fermi Liquid" form, postulated to describe the optimally doped cuprates.