  We propose a time-reversal-even spin generation in second order of electric
fields, which dominates the current induced spin polarization in a wide class
of centrosymmetric nonmagnetic materials, and leads to a novel nonlinear
spin-orbit torque in magnets. We reveal a quantum origin of this effect from
the momentum space dipole of the anomalous spin polarizability.
First-principles calculations predict sizable spin generations in several
nonmagnetic hcp metals, in monolayer TiTe$_{2}$, and in ferromagnetic monolayer
MnSe$_{2}$, which can be detected in experiment. Our work opens up the broad
vista of nonlinear spintronics in both nonmagnetic and magnetic systems.
