Absence of disorder-driven metal-insulator transitions in simple holographic models

TL;DR

This paper investigates electrical transport in strongly coupled strange metals using holography, demonstrating a universal lower bound on conductivity and providing new hydrodynamic insights into disorder effects.

Contribution

It proves a universal minimal conductivity bound in holographic strange metals and advances understanding of disorder effects through hydrodynamic methods.

Findings

Electrical conductivity is bounded below by a universal quantum critical value.

Disorder does not induce a metal-insulator transition in these models.

Hydrodynamic approaches effectively analyze holographic transport phenomena.

Abstract

We study electrical transport in a strongly coupled strange metal in two spatial dimensions at finite temperature and charge density, holographically dual to Einstein-Maxwell theory in an asymptotically $\mathrm{AdS}_4$ spacetime, with arbitrary spatial inhomogeneity, up to mild assumptions including emergent isotropy. In condensed matter, these are candidate models for exotic strange metals without long-lived quasiparticles. We prove that the electrical conductivity is bounded from below by a universal minimal conductance: the quantum critical conductivity of a clean, charge-neutral plasma. Beyond non-perturbatively justifying mean-field approximations to disorder, our work demonstrates the practicality of new hydrodynamic insight into holographic transport.