Characterization of the magnetic field through the three-body loss near a narrow Feshbach resonance

TL;DR

This paper presents a method to accurately measure magnetic fields near a narrow Feshbach resonance by correcting eddy current effects through analyzing three-body loss dynamics in a $^6$Li Fermi gas.

Contribution

The authors develop a correction technique for eddy current delays, enabling precise magnetic field measurements using three-body loss data near a narrow Feshbach resonance.

Findings

Eddy current effects cause measurable delays in magnetic field changes.

The correction method accurately determines the actual magnetic field.

Three-body recombination dominates atom loss near the resonance.

Abstract

The narrow s-wave Feshbach resonance of a $^6$Li Fermi gas shows strong three-body loss, which is proposed to be used to measure the minute change of a magnetic field around the resonance. However, the eddy current will cause ultracold atom experiencing a magnetic field delayed to the desired magnetic field from the current of the magnetic coils. The elimination of the eddy current effect will play a key role in any experiments that motivated to measure the magnetic field to the precision of a part per million stability. Here, we apply a method to correct the eddy current effect for precision measurement of the magnetic field. We first record the three-body loss influenced by the effect of induced eddy current, then use a certain model to obtain the time constant of the actual magnetic field by fitting the atom loss. This precisely determines the actual magnetic field according to the time response of the three-body loss. After that, we implement the desired magnetic field to the atoms so that we can analyze the three-body loss across the whole narrow Feshbach resonance. The results show that the three-body recombination is the dominated loss mechanism near the resonance. We expect this practical method of correcting the eddy current error of the magnetic field can be further applied to the future studies of quantum few- and many-body physics near a narrow Feshbach resonance.