AC conductivities of a holographic Dirac semimetal

TL;DR

This paper uses holographic duality to compute the frequency-dependent AC conductivities of a strongly coupled (2+1)-dimensional Dirac semimetal model with finite charge density, magnetic and electric fields, revealing phase-dependent transport properties.

Contribution

It provides the first detailed holographic calculation of AC conductivities in a Dirac semimetal model with competing chiral symmetry phases at finite density and external fields.

Findings

Derived the full frequency dependence of longitudinal and Hall conductivities.

Identified phase-dependent differences in conductivity behavior.

Demonstrated the impact of electric and magnetic fields on transport properties.

Abstract

We use the AdS/CFT correspondence to compute the AC conductivities for a (2+1)-dimensional system of massless fundamental fermions coupled to (3+1)-dimensional Super Yang-Mills theory at strong coupling. We consider the system at finite charge density, with a constant electric field along the defect and an orthogonal magnetic field. The holographic model we employ is the well studied D3/probe-D5-brane system. There are two competing phases in this model: a phase with broken chiral symmetry favored when the magnetic field dominates over the charge density and the electric field and a chirally symmetric phase in the opposite regime. The presence of the electric field induces Ohm and Hall currents, which can be straightforwardly computed by means of the Karch-O'Bannon technique.Studying the fluctuations around the stable configurations in linear response theory, we are able to derive the full frequency dependence of longitudinal and Hall conductivities in all the regions of the phase space.