Magnetoconductivity of Dirac semimetals and chiral magnetic effect from Keldysh technique

Negative magnetoresistance in Dirac semimetals is typically considered as a manifestation of chiral magnetic effect. The relation between these two phenomena has the status of a hypothesis and is based on sequence of assumptions. We rely on the Keldysh technique of non-equilibrium theory. It allows us to investigate the accumulation of axial charge-the process that involves chiral anomaly and relaxation followed by the energy dissipation. We consider the case of strong magnetic field and calculate directly axial charge density and electric conductivity, taking into account scattering on impurities and interaction with phonons. Overall, our analysis is consistent with the CME-based analysis of magnetoconductivity in Dirac semimetals in the limit of strong magnetic fields. We obtain the same relation between axial charge density and electric and magnetic fields, as well as between electric current and axial charge density as the standard heuristic CME calculation. But we also calculate the relaxation time as a function of model parameters, instead of introducing the relaxation time as a free parameter.