Calibration of Interaction Energy between Bose and Fermi Superfluids

TL;DR

This paper investigates the interaction energy between Bose and Fermi superfluids in cold atom experiments, calculating the atom-dimer scattering length and providing a calibration method for mean-field interaction energy based on three-body analysis.

Contribution

The study introduces a detailed three-body analysis including van der Waals effects to accurately determine atom-dimer scattering length, improving upon mean-field approximations.

Findings

Significant deviation from mean-field predictions in atom-dimer scattering length.

Multiple scattering effects explain the deviation from mean-field results.

Calibration method for mean-field interaction energy via collective oscillation measurements.

Abstract

In this letter we study the interaction energy in a mixture of Bose and Fermi superfluids realized in recent cold atom experiment. On the Bose-Einstein-condensate (BEC) side of a Feshbach resonance between fermionic atoms, this interaction energy can be directly related to the scattering length between a bosonic atom and a dimer composed of fermions. We calculate the atom-dimer scattering length from a three-body analysis with both a zero-range model and a separable model including the van der Waals length scale, and we find significant deviation from the result given by a mean-field approach. We also find that the multiple scattering between atom and dimer can account for such a deviation. Our results provide a calibration to the mean-field interaction energy, which can be verified by measuring the shift of collective oscillation frequency.