Negative magnetoresistivity in chiral fluids and holography

TL;DR

This paper investigates the longitudinal magnetoconductivity in chiral fluids with a magnetic field, revealing conditions for finite conductivity, matching hydrodynamic and holographic calculations, and explaining experimental magnetoresistivity behaviors.

Contribution

It provides a combined hydrodynamic and holographic analysis of magnetoconductivity in chiral systems, highlighting the role of dissipation and quantum criticality.

Findings

Finite DC longitudinal magnetoconductivity requires energy, momentum, and charge dissipation.

Hydrodynamic and holographic results agree in the regime studied.

Holography explains the small B positive magnetoresistivity observed experimentally.

Abstract

In four dimensions Weyl fermions possess a chiral anomaly which leads to several special features in the transport phenomena, such as the negative longitudinal magnetoresistivity. In this paper, we study its inverse, the longitudinal magnetoconductivity, in the case of a chiral anomalous system with a background magnetic field B using the linear response method in the hydrodynamic limit and from holography. Our hydrodynamic results show that in general we need to have energy, momentum and charge dissipations to get a finite DC longitudinal magnetoconductivity due to the existence of the chiral anomaly. Applying the formula that we get from hydrodynamics to the holographic system in the probe limit, we find that the result in the hydrodynamic regime matches that calculated from holography via Kubo formula. The holographic result shows that in an intermediate regime of B there is naturally a negative magnetoresistivity which decreases as 1/B. At small B direct calculations in the holographic system suggest that holography provides a new explanation for the small B positive magnetoresistivity behavior seen in experiment, i.e. the small B behavior comes from the quantum critical conductivity being affected by the chiral anomaly.