Macroscopic random Paschen-Back effect in ultracold atomic gases

Abstract

We consider spin- and density-related properties of single-particle states in a one-dimensional system with random spin-orbit coupling. We show that the presence of an additional Zeeman field $\Delta$ induces both nonlinear spin polarization and delocalization of states localized at $\Delta=0$, corresponding to a random macroscopic analogue of the Paschen-Back effect. While the conventional Paschen-Back effect corresponds to a saturated $\Delta-$dependence of the spin polarization, here the gradual suppression of the spin-orbit coupling effects by the Zeeman field is responsible both for the spin saturation and delocalization of the particles.