Photon drag current due to spin-flip transitions of electrons in nonsymmetric quantum wells

Photon drag current caused by transfer of momentum from absorbed far-infrared radiation to two-dimensional (2D) electrons is calculated for spin-flip transitions in nonsymmetric heterostructures. The induced current is not parallel to the longitudinal component of photon wave vector $\mathbf{q}$ because the contribution $[\mathbf{q}\times {\mathbf{v}}_s]$ $({\mathbf{v}}_s$ is the characteristic spin velocity along the normal to 2D layer) is essential in the matrix element for spin-flip electron-photon interaction. Both spectral and angular dependencies of the current and the effect of the in-plane magnetic field are discussed for the short-range scattering case. Numerical estimations for typical parameters of InAs-based heterostructures and a THz pump with intensity $1\hspace{0.5em}{\mathrm{k}\mathrm{W}/\mathrm{c}\mathrm{m}}^2$ are presented.