# Macroscopic random Paschen-Back effect in ultracold atomic gases

## TL;DR

This paper demonstrates a macroscopic analogue of the Paschen-Back effect in ultracold atomic gases, showing how a Zeeman field induces spin polarization and delocalization in a system with random spin-orbit coupling.

## Contribution

It introduces the concept of a macroscopic Paschen-Back effect in ultracold gases, linking Zeeman fields to spin and localization properties in disordered systems.

## Key findings

- Zeeman field induces nonlinear spin polarization.
- Zeeman field causes delocalization of localized states.
- Spin saturation occurs due to suppression of spin-orbit effects.

## 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.