A Feshbach resonance in d-wave collisions

TL;DR

This paper investigates a narrow d-wave Feshbach resonance in ultra-cold chromium atoms caused by dipole-dipole interactions, analyzing its properties, experimental data, and theoretical modeling to understand three-body losses and resonance characteristics.

Contribution

The study provides the first detailed analysis of a dipole-dipole induced d-wave Feshbach resonance, including experimental measurements and theoretical calculations with no adjustable parameters.

Findings

Three-body loss rates increase with temperature.

Loss feature width scales linearly with temperature.

Good agreement between experimental data and dipole-dipole interaction calculations.

Abstract

We analyse a narrow Feshbach resonance with ultra-cold chromium atoms colliding in d-wave. The resonance is made possible by dipole-dipole interactions, which couple an incoming $l=2$ collision channel with a bound molecular state with $l=0$. We find that three-body losses associated to this resonance increase with temperature, and that the loss feature width as a function of magnetic field also increases linearly with temperature. The analysis of our experimental data shows that the Feshbach coupling is small compared both to the temperature and to the density limited lifetime of the resonant bound molecular state. One consequence is that the three body losse rate is proportionnal to the square of the number of atoms, and that we can directly relate the amplitude of the losses to the Feshbach coupling parameter. We compare our measurement to a calculation of the coupling between the collisionnal channel and the molecular bound state by dipole-dipole interactions, and find a good agreement, with no adjustable parameter. An analysis of the loss lineshape is also performed, which enables to precisely measure the position of the resonance.