Local electric current correlation function in an exponentially decaying magnetic field

TL;DR

This paper investigates how an exponentially decaying magnetic field affects Dirac fermions in 3+1 dimensions, deriving the energy spectrum analytically and analyzing local electric current correlations in the lowest Landau level approximation.

Contribution

It provides an analytical solution for the fermion energy spectrum in an inhomogeneous magnetic field and examines quantum corrections to the local current correlations.

Findings

Energy spectrum determined analytically using Ritus method.

Chiral condensate and local current correlations computed in LLL approximation.

Limits to constant magnetic field are singular when quantum corrections are included.

Abstract

The effect of an exponentially decaying magnetic field on the dynamics of Dirac fermions in 3+1 dimensions is explored. The spatially decaying magnetic field is assumed to be aligned in the third direction, and is defined by {\mathbf{B}}(x)=B(x){\mathbf{e}}_{z}, with B(x)=B_{0}e^{-\xi\ x/\ell_{B}}. Here, \xi\ is a dimensionless damping factor and \ell_{B}=(eB_{0})^{-1/2} is the magnetic length. As it turns out, the energy spectrum of fermions in this inhomogeneous magnetic field can be analytically determined using the Ritus method. Assuming the magnetic field to be strong, the chiral condensate and the \textit{local} electric current correlation function are computed in the lowest Landau level (LLL) approximation and the results are compared with those arising from a strong homogeneous magnetic field. Although the constant magnetic field B_{0} can be reproduced by taking the limit of \xi-> 0 and/or x-> 0 from B(x), these limits turn out to be singular once the quantum corrections are taken into account.