Nonlinear chiral transport from holography

TL;DR

This paper uses holography to analyze nonlinear chiral transport phenomena in a 4D field theory, deriving numerous transport coefficients and discovering new effects like the Chiral Hall Density Wave.

Contribution

It provides the first comprehensive analytical computation of over 50 nonlinear transport coefficients induced by the chiral anomaly in a holographic model.

Findings

Derived general form of vector and axial currents under electromagnetic fields.

Computed over 50 nonlinear transport coefficients up to third order.

Discovered a new gapless mode called Chiral Hall Density Wave.

Abstract

Nonlinear transport phenomena induced by the chiral anomaly are explored within a 4D field theory defined holographically as $U(1)_V\times U(1)_A$ Maxwell-Chern-Simons theory in Schwarzschild-$AdS_5$. First, in presence of external electromagnetic fields, a general form of vector and axial currents is derived. Then, within the gradient expansion up to third order, we analytically compute all (over 50) transport coefficients. A wealth of higher order (nonlinear) transport phenomena induced by chiral anomaly are found beyond the Chiral Magnetic and Chiral Separation Effects. Some of the higher order terms are relaxation time corrections to the lowest order nonlinear effects. The charge diffusion constant and dispersion relation of the Chiral Magnetic Wave are found to receive anomaly-induced non-linear corrections due to e/m background fields. Furthermore, there emerges a new gapless mode, which we refer to as {\it Chiral Hall Density Wave}, propagating along the background Poynting vector.