Magnetically tunable Feshbach resonances in ultracold gases of europium atoms and mixtures of europium and alkali-metal atoms

TL;DR

This paper explores magnetically tunable Feshbach resonances in ultracold europium atoms and their mixtures with alkali-metal atoms, revealing feasible control over scattering properties and potential for quantum gas applications.

Contribution

It provides the first detailed multichannel quantum scattering analysis of Feshbach resonances in europium systems, including heteronuclear mixtures with alkali metals, highlighting their experimental accessibility.

Findings

Resonances are expected below 1000 G for all systems.

Europium exhibits a rich resonance spectrum due to competing interactions.

High resonance density below 200 G with minimal quantum chaos signatures.

Abstract

We investigate magnetically tunable Feshbach resonances between ultracold europium atoms and between europium and alkali-metal atoms using multichannel quantum scattering calculations. For ultracold gases of europium atoms both homonuclear $^{153}$Eu+$^{153}$Eu and heteronuclear $^{151}$Eu+$^{153}$Eu systems are studied. Calculations for mixtures of europium and alkali-metal atoms are carried out for prototype systems of $^{153}$Eu+$^{87}$Rb and $^{153}$Eu+$^7$Li. We analyze the prospects for the control of scattering properties, observation of quantum chaotic behavior, and magnetoassociation into ultracold polar and paramagnetic molecules. We show that favorable resonances can be expected at experimentally feasible magnetic field strengths below 1000$\,$G for all investigated atomic combinations. For Eu atoms, a rich spectrum of resonances is expected as a result of the competition between relatively weak short-range spin-exchange and strong long-range magnetic dipole-dipole interactions, where the dipolar interaction induces measurable resonances. A high density of resonances is expected at magnetic field strengths below 200$\,$G without pronounced quantum chaos signatures. The present results may be useful for the realization and application of dipolar atomic and molecular quantum gases based on europium atoms in many-body physics.