On holographic disorder-driven metal-insulator transitions

TL;DR

This paper introduces a holographic model for disorder-driven metal-insulator transitions, showing how disorder can drastically reduce electrical conductivity and potentially lead to new phases.

Contribution

It develops a minimal holographic framework incorporating disorder effects via Massive Gravity, revealing how disorder influences conductivity and phase stability.

Findings

Disorder decreases DC electrical conductivity in the model.

Conductivity can become arbitrarily small, indicating insulating behavior.

Large disorder may cause gradient instabilities, suggesting modulated phases.

Abstract

We give a minimal holographic model of a disorder-driven metal-insulator transition. It consists in a CFT with a charge sector and a translation-breaking sector that interact in the most generic way allowed by the symmetries and by dynamical consistency. In the gravity dual, it reduces to a Massive Gravity-Maxwell model with new direct couplings between the Maxwell and metric that are allowed when gravity is massive. We show that, generically, the effect of disorder is to decrease the DC electrical conductivity. This happens to such an extent that the conductivity does not obey any lower bound and can be very small in the insulating phase. In some cases, the large disorder limit produces gradient instabilities that hint at the formation of modulated phases.