Probing Ferromagnetic Order in Few-Fermion Correlated Spin-Flip Dynamics

TL;DR

This paper investigates the stability and emergence of ferromagnetic order in a few-fermion one-dimensional ultracold gas under inhomogeneous spin driving, revealing regimes where spins become almost maximally aligned despite overall polarization decay.

Contribution

It demonstrates the existence of an interaction regime where spin correlations induce near-maximal ferromagnetic order in a dynamically evolving few-fermion system, supported by single-shot simulation predictions.

Findings

Identification of a regime with strong spin correlations leading to ferromagnetic order.

Observation of a decay in total spin-polarization over time.

Prediction that these phenomena can be observed in current ultracold atom experiments.

Abstract

We unravel the dynamical stability of a fully polarized one-dimensional ultracold few-fermion spin-1/2 gas subjected to inhomogeneous driving of the itinerant spins. Despite the unstable character of the total spin-polarization the existence of an interaction regime is demonstrated where the spin-correlations lead to almost maximally aligned spins throughout the dynamics. The resulting ferromagnetic order emerges from the build up of superpositions of states of maximal total spin. They comprise a decaying spin-polarization and a dynamical evolution towards an almost completely unpolarized NOON-like state. Via single-shot simulations we demonstrate that our theoretical predictions can be detected in state-of-the-art ultracold experiments.