Fermionization of two-component few-fermion systems in a one-dimensional harmonic trap

TL;DR

This paper investigates the behavior of two-component fermionic systems in a one-dimensional harmonic trap, revealing that strong interactions lead to spatial separation of spins, indicating a precursor to ferromagnetism in ultracold atomic experiments.

Contribution

The study introduces a new effective-interaction technique and analytical approach to analyze few-fermion systems, providing insights into magnetic correlations and spin separation under strong interactions.

Findings

Strong interactions cause spin separation in the trap.

The results suggest a microscopic precursor to 1D ferromagnetism.

Predictions are experimentally accessible with ultracold gases.

Abstract

The nature of strongly interacting Fermi gases and magnetism is one of the most important and studied topics in condensed-matter physics. Still, there are many open questions. A central issue is under what circumstances strong short-range repulsive interactions are enough to drive magnetic correlations. Recent progress in the field of cold atomic gases allows to address this question in very clean systems where both particle numbers, interactions and dimensionality can be tuned. Here we study fermionic few-body systems in a one dimensional harmonic trap using a new rapidly converging effective-interaction technique, plus a novel analytical approach. This allows us to calculate the properties of a single spin-down atom interacting with a number of spin-up particles, a case of much recent experimental interest. Our findings indicate that, in the strongly interacting limit, spin-up and spin-down particles want to separate in the trap, which we interpret as a microscopic precursor of one-dimensional ferromagnetism in imbalanced systems. Our predictions are directly addressable in current experiments on ultracold atomic few-body systems.