Decoherence via induced dipole collisions in an ultracold gas

TL;DR

This study investigates how heteronuclear induced dipole-dipole collisions between different rubidium isotopes in an ultracold gas reduce laser cooling efficiency and trap loading, highlighting a decoherence mechanism affecting ultracold atom experiments.

Contribution

It provides experimental evidence and theoretical estimates that heteronuclear induced dipole interactions cause decoherence, disrupting optical trap loading in ultracold rubidium gases.

Findings

Loading rate decreases with $^{85}$Rb presence

Heteronuclear dipole collisions disrupt ground-state coherences

Loss of cooling efficiency linked to induced dipole interactions

Abstract

We have studied the effects of loading $^{87}$Rb into a far off resonant trap (FORT) in the presence of an ultracold cloud of $^{85}$Rb. The presence of the $^{85}$Rb resulted in a marked decrease of the $^{87}$Rb load rate. This decrease is consistent with a decrease in the laser cooling efficiency needed for effective loading. While many dynamics which disrupt loading efficency arise when cooling in a dense cloud of atoms (reabsorption, adverse optical pumping, etc.), the large detuning between the transitions of $^{85}$Rb and $^{87}$Rb should isolate the isotopes from these effects. For our optical molasses conditions we calculate that our cooling efficiencies require induced ground-state coherences. We present data and estimates which are consistent with heteronuclear long-ranged induced dipole-dipole collisions disrupting these ground state coherences, leading to a loss of optical trap loading efficiency.