Localized chiral magnetic effect in equilibrium QCD

We study the impact of a nonuniform magnetic background field on the chiral magnetic effect (CME) in equilibrium QCD using lattice simulations with <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>2</a:mn><a:mo>+</a:mo><a:mn>1</a:mn></a:mrow></a:math> flavors of dynamical staggered quarks at the physical point. We show that in the presence of a nonuniform magnetic field the CME manifests itself via a localized electromagnetic current density along the direction of the field, which integrates to zero over the full volume. Our primary observable is the leading-order coefficient of the current in a chiral chemical potential expansion, which we compute for various lattice spacings and extrapolate to the continuum limit. Our findings demonstrate that, even though the global spatial average of the CME conductivity vanishes in equilibrium, steady currents still exist locally. Thus, spatially modulated magnetic fields provide a possible way of generating a nontrivial CME signal in equilibrium.