Modified Drude–Lorentz model taking into account topological medium characteristics

The Drude–Lorentz model, which allows to describe nonlinear response of dielectric or conduc-tor, could be used for describing nonlinear non resonant responses of some exotic media, such as the topological insulators, the Weyl semimetals and the Dirac metals. Generalized Drude–Lorentz model and its simplified version, where the topological effects are taken into account in the minimal order, are presented in paper. A nonlinear conductance of the second order corre-sponding to second harmonic generation and optical rectification effect is obtained in paper as an example of use of the simplified model. It is shown that the ratio of the topological conductance to the ordinary linear conductance contains the constant value that is proportional to the fine structure constant and axion field gradient.