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Anomalous Hall effect in ultraclean electronic channels

Recent technological advances allow fabricating ultraclean two-dimensional electronic systems where the electron mean free path due to static disorder and phonons is much larger compared to the conducting channel width. It makes possible to realize novel, ballistic and hydrodynamic, regimes of electron transport resulting in drastic modifications of the normal Hall effect. Here we develop a theory of anomalous Hall effect -- generation of the electric field transverse to the flowing current unrelated to the Lorentz force action -- in ultraclean channels with two-dimensional electron gas and demonstrate that both in ballistic and hydrodynamic regimes the anomalous Hall effect, similarly to the normal one, strongly differs from that in the standard diffusive case. We take into account all relevant contributions to the anomalous Hall electric field and Hall voltage: the skew scattering of electrons, side-jump, and anomalous velocity effects that appear as a result of the spin-orbit coupling. We study both ballistic and hydrodynamic transport regimes which are realized depending on the relation between the electron-electron mean free path and the channel width. The role of electron-electron interactions is analyzed. Compact analytical expressions for the anomalous Hall field and voltage are derived. Possible experimental scenarios for observation of the anomalous Hall effect in ultraclean channels are briefly discussed.