Nonlinear adiabatic passage from fermion atoms to boson molecules

TL;DR

This paper investigates the dynamics of converting fermionic atoms to bosonic molecules via adiabatic Feshbach resonance sweeps, revealing many-body effects and different scaling behaviors depending on initial conditions.

Contribution

It provides a detailed analysis of the nonlinear many-body dynamics during atom-molecule conversion, highlighting deviations from simple Landau-Zener predictions.

Findings

Atomic fraction dependence on sweep rate varies from exponential to power-law with particle number.

Linear dependence when initial molecular fraction is below quantum fluctuations.

Experimental data favor many-body models over single-pair Landau-Zener predictions.

Abstract

We study the dynamics of an adiabatic sweep through a Feshbach resonance in a quantum gas of fermionic atoms. Analysis of the dynamical equations, supported by mean-field and many-body numerical results, shows that the dependence of the remaining atomic fraction $\Gamma$ on the sweep rate $\alpha$ varies from exponential Landau-Zener behavior for a single pair of particles to a power-law dependence for large particle number $N$. The power-law is linear, $\Gamma \propto \alpha$, when the initial molecular fraction is smaller than the 1/N quantum fluctuations, and $\Gamma \propto \alpha^{1/3}$ when it is larger. Experimental data agree better with a linear dependence than with an exponential Landau-Zener fit, indicating that many-body effects are significant in the atom-molecule conversion process.