Quenching of the spin Hall effect in ballistic nanojunctions

We show that a nanometric four-probe ballistic junction can be used to check the presence of a transverse spin Hall current in a system with a spin orbit coupling not of the Rashba type, but rather due to the in-plane electric field. Indeed, the spin Hall effect is due to the presence of an effective small transverse magnetic field corresponding to the spin orbit coupling generated by the confining potential. The strength of the field and the junction shape characterize the quenching Hall regime, usually studied by applying semiclassical approaches. We discuss how a quantum mechanical relativistic effect, such as the spin orbit one, can be observed in a low energy system and explained by using classical mechanics techniques.