Extrinsic and intrinsic ratchet response of a quantum dissipative spin-orbit medium
Traditionally the charge ratchet effect is considered as a consequence of the extrinsic spatial asymmetry engineered by external asymmetric periodic potentials. Here we demonstrate that electrically and magnetically driven dissipative systems with spin-orbit interactions represent an exception from this standard idea. The charge and spin ratchet currents appear just due to the coexistence of quantum dissipation with the intrinsic spatial asymmetry of the spin-orbit coupling. The extrinsic spatial asymmetry is inessential.