Anisotropic electron transport Rashba effects in valleytronics

Electrically induced space separation of free carriers of different valleys in bulk multivalley semiconductors with restricted geometry was first reported by Rashba in 1965. This Rashba's size effect remains relevant at the present time for the rapidly developing field of valleytronics. In this paper, we investigate theoretically electrically induced formation of valley-polarized free-carrier domains in two-dimensional (2D) many-valley semiconductor nanosystems with equivalent anisotropic valleys such as in n-Si, n-AlAs, etc. The domains are well-resolved spatial regions in which the electrons of only one of the valleys are present, thereby providing a pure bulk valley current inside the considered domain region. The domain properties including the polarization amplitude, the domain wall width, configurations of the induced transverse electric fields, valley currents, and the excess electric charge density are analyzed as a function of the applied electric field E. The valley-polarized domains in the nanostrip generate inhomogeneous electrostatic potential outside the strip and give rise to strati-fication of the induced by the current magnetic field consistent with the valley-polarized domains. These effects facilitate experimental verification of the valley polarization by the existing methods of scanning nanoscale imaging. We suggest that the study of electrically induced domains of valley polarization in 2D nanosystems brings new knowledge on valley physics and can be used in valleytronics applications.