Effective holographic theories of momentum relaxation and violation of conductivity bound

TL;DR

This paper extends holographic models with higher derivative couplings to study charge transport and shows that the DC conductivity can vanish at zero temperature, challenging the notion of a universal conductivity bound.

Contribution

It introduces higher derivative couplings in holographic models with translation symmetry breaking and derives analytical solutions for charge transport properties.

Findings

DC conductivity can vanish at zero temperature

No universal lower bound on conductivity

Analytical charged black brane solutions obtained

Abstract

We generalize current holographic models with homogeneous breaking of translation symmetry by incorporating higher derivative couplings, in the spirit of effective field theories. Focusing on charge transport, we specialize to two simple couplings between the charge and translation symmetry breaking sectors. We obtain analytical charged black brane solutions and compute their DC conductivity in terms of horizon data. We constrain the allowed values of the couplings and note that the DC conductivity can vanish at zero temperature for strong translation symmetry breaking, thus showing that in general there is no lower bound on the conductivity.