On Effective Holographic Mott Insulators

TL;DR

This paper introduces holographic models mimicking Mott insulators using non-linear electrodynamics, revealing key transport features, phase transitions, and nonlinear electrical responses characteristic of strongly correlated electron systems.

Contribution

It develops a new holographic framework for Mott insulators incorporating self-interacting gauge fields, capturing their transport and phase transition behaviors.

Findings

Low-temperature DC conductivity is very low.

Metal-insulator transitions can be triggered by parameter changes.

Nonlinear response shows reduced conductivity at high voltages.

Abstract

We present a class of holographic models that behave effectively as prototypes of Mott insulators, materials where electron-electron interactions dominate transport phenomena. The main ingredient in the gravity dual is that the gauge-field dynamics contains self-interactions by way of a particular type of non-linear electrodynamics. The electrical response in these models exhibits typical features of Mott-like states: i) the low-temperature DC conductivity is unboundedly low; ii) metal-insulator transitions appear by varying various parameters; iii) for large enough self-interaction strength, the conductivity can even decrease with increasing doping (density of carriers), which appears as a sharp manifestation of `traffic-jam'-like behaviour; iv) the insulating state becomes very unstable towards superconductivity at large enough doping. We exhibit some of the properties of the resulting insulator-superconductor transition, which is sensitive to the amount of disorder in a specific way. These models imply a clear and generic correlation between Mott behaviour and significant effects in the nonlinear electrical response. We compute the nonlinear current-voltage curve in our model and find that indeed at large voltage the conductivity is largely reduced.