# Pair formation in quenched unitary Bose gases

## TL;DR

This paper investigates how a quenched unitary Bose gas develops many-body-induced pairs, revealing a process similar to Cooper pairing, with results aligning with experiments for fast sweeps but highlighting the need for higher-order effects in other regimes.

## Contribution

It introduces a many-body model including three-body losses to describe pair formation in quenched Bose gases, demonstrating a phenomenon analogous to Cooper pairing.

## Key findings

- Formation of extended pairs due to many-body correlations.
- Quantitative agreement with experiments for fast sweeps.
- Deviations at slower sweeps suggest higher-order effects are important.

## Abstract

We study a degenerate Bose gas quenched to unitarity by solving a many-body model including three-body losses and correlations up to second order. As the gas evolves in this strongly-interacting regime, the buildup of correlations leads to the formation of extended pairs bound purely by many-body effects, analogous to the phenomenon of Cooper pairing in the BCS regime of the Fermi gas. Through fast sweeps away from unitarity, we detail how the correlation growth and formation of bound pairs emerge in the fraction of unbound atoms remaining post sweep, finding quantitative agreement with experiment. We comment on the possible role of higher-order effects in explaining the deviation of our theoretical results from experiment for slower sweeps and longer times spent in the unitary regime.