Isotopic shift of atom-dimer Efimov resonances in K-Rb mixtures: Critical effect of multichannel Feshbach physics

TL;DR

This paper investigates how multichannel Feshbach physics influences Efimov resonances in heteronuclear K-Rb mixtures, revealing a measurable isotopic shift explained by a three-body model including van der Waals and multichannel effects.

Contribution

It demonstrates the critical role of multichannel Feshbach physics in determining Efimov resonance positions in heteronuclear atom-dimer systems, supported by experimental observations and theoretical modeling.

Findings

Observed isotopic shift in atom-dimer resonance positions.

The shift is explained by multichannel Feshbach physics and three-body calculations.

Highlights the importance of multichannel effects in heteronuclear Efimov physics.

Abstract

The multichannel Efimov physics is investigated in ultracold heteronuclear admixtures of K and Rb atoms. We observe a shift in the scattering length where the first atom-dimer resonance appears in the $^{41}$K-$^{87}$Rb system relative to the position of the previously observed atom-dimer resonance in the $^{40}$K-$^{87}$Rb system. This shift is well explained by our calculations with a three-body model including the van der Waals interactions, and, more importantly, the multichannel spinor physics. With only minor difference in the atomic masses of the admixtures, the shift in the atom-dimer resonance positions can be cleanly ascribed to the isolated and overlapping Feshbach resonances in the $^{40}$K-$^{87}$Rb and $^{41}$K-$^{87}$Rb systems, respectively. Our study demonstrates the role of the multichannel Feshbach physics in determining Efimov resonances in heteronuclear three-body systems.