From Few to Many: Observing the Formation of a Fermi Sea One Atom at a Time

TL;DR

This study explores how a system of ultracold atoms transitions from few-body to many-body physics by measuring interaction energies as the number of particles increases, revealing rapid convergence to many-body behavior.

Contribution

It provides experimental evidence of the crossover from few to many-body physics in ultracold atom systems, demonstrating the formation of a Fermi sea one atom at a time.

Findings

Normalized interaction energy converges quickly to many-body limit.

Interaction energy depends on the number of majority atoms and interaction strength.

Observation of the formation of a Fermi sea from single impurity to many particles.

Abstract

Knowing when a physical system has reached sufficient size for its macroscopic properties to be well described by many-body theory is difficult. We investigate the crossover from few to many-body physics by studying quasi one-dimensional systems of ultracold atoms consisting of a single impurity interacting with an increasing number of identical fermions. We measure the interaction energy of such a system as a function of the number of majority atoms for different strengths of the interparticle interaction. As we increase the number of majority atoms one by one we observe the fast convergence of the normalized interaction energy towards a many-body limit calculated for a single impurity immersed in a Fermi sea of majority particles.