ABSTRACT
Spin generation and spin currents in semiconductor structures lie at the heart of the emerging ¢eld of spintronics and are a major and still-growing direction of solid-state research. Among the plethora of concepts and ideas, current-induced spin polarization (CISP) has attracted particular interest from both experimental and theoretical point of view, for reviews see Refs. [1-9]. In nonmagnetic semiconductors or metals belonging to the gyrotropic point groups,* dc electric current is generically accompanied by a nonzero average nonequilibrium spatially homogeneous spin polarization and vice versa. že latter phenomenon is referred to as the spin-galvanic e¥ect (see, e.g., Refs. [5,7,10-13]). In low-dimensional semiconductor structures, these e¥ects are caused by asymmetric spin relaxation in systems with liªed spin degeneracy due to k-linear terms in the Hamiltonian, where k is the electron wave vector. In spite of the terminological resemblance, spin polarization by electric current fundamentally di¥ers from the spin Hall e¥ect [4-6,8,14-20], which refers to the generation of a pure spin current transverse to the charge current and causes spin accumulation at the sample edges. že
distinctive features of the CISP are that this e¥ect can be present in gyrotropic media only, it results in nonzero average spin polarization, and does not depend on the space coordinates. žus, it can be measured in the whole sample under appropriate conditions. že spin Hall e¥ect, in contrast, does not yield average spin polarization and does not require gyrotropy, at least for the extrinsic spin Hall e¥ect.
