Holographic pinning

TL;DR

This paper demonstrates holographic pinning by explicitly breaking translational symmetry in a probe-brane model, showing how Goldstone modes are lifted and analyzing the resulting optical conductivity and phase stability.

Contribution

It introduces explicit symmetry-breaking sources into a holographic model to achieve pinning, a first in such models, and analyzes the effects on conductivity and phase stability.

Findings

Goldstone mode is lifted by explicit symmetry breaking.

Optical conductivity matches Drude-Lorentz model with residual metallicity.

Large ionic lattice causes instability in striped phase.

Abstract

In a holographic probe-brane model exhibiting a spontaneously spatially modulated ground state, we introduce explicit sources of symmetry breaking in the form of ionic and antiferromagnetic lattices. For the first time in a holographic model, we demonstrate pinning, in which the translational Goldstone mode is lifted by the introduction of explicit sources of translational symmetry breaking. The numerically computed optical conductivity fits very well to a Drude-Lorentz model with a small residual metallicity, precisely matching analytic formulas for the DC conductivity. We also find an instability of the striped phase in the presence of a large-amplitude ionic lattice.