# Cluster formation in two-component Fermi gases

## TL;DR

This paper investigates the conditions under which cluster states form in two-component Fermi gases, revealing that a sufficiently large effective range of interaction leads to clustering, with implications for experimental observation.

## Contribution

It identifies a universal threshold for cluster formation based on the effective range of interactions, advancing understanding of few-body physics in Fermi gases.

## Key findings

- Cluster states form when the effective range exceeds ~0.46 times the scattering length.
- Structural differences between cluster and gas-like states are characterized.
- The study provides conditions for experimental detection of cluster states.

## Abstract

Two-component fermions are known to behave like a gas of molecules in the limit of Bose-Einstein condensation of diatomic pairs tightly bound with zero-range interactions. We discover that the formation of cluster states occurs when the effective range of two-body interaction exceeds roughly $0.46$ times the scattering length, regardless of the details of the short-range interaction. Using explicitly correlated Gaussian basis set expansion approach, we calculate the binding energy of cluster states in trapped few-body systems and show the difference of structural properties between cluster states and gas-like states. We identify the condition for cluster formation and discuss potential observation of cluster states in experiments.