An ionic impurity in a Bose-Einstein condensate at sub-microkelvin temperatures

TL;DR

This paper demonstrates the observation of ion-atom interactions at sub-microkelvin temperatures using Rydberg atoms in a Bose-Einstein condensate, revealing new insights into charged quantum impurities.

Contribution

It introduces a method to suppress electron-neutral interactions, enabling the study of ion-atom interactions in a quantum gas at ultra-low temperatures.

Findings

Clear evidence of ion-atom interaction at sub-microkelvin temperatures

Rydberg orbit exceeds the size of the atomic sample

Potential to explore charged quantum impurities and polaron physics

Abstract

Rydberg atoms immersed in a Bose-Einstein condensate interact with the quantum gas via electron-atom and ion-atom interaction. To suppress the typically dominant electron-neutral interaction, Rydberg states with principal quantum number up to $n = 190$ are excited from a dense and tightly trapped micron-sized condensate. This allows us to explore a regime where the Rydberg orbit exceeds the size of the atomic sample by far. In this case, a detailed lineshape analysis of the Rydberg excitation spectrum provides clear evidence for ion-atom interaction at temperatures well below a microkelvin. Our results may open up ways to enter the quantum regime of ion-atom scattering for the exploration of charged quantum impurities and associated polaron physics.