Contact Measurements on Atomic BEC

TL;DR

This paper reports measurements of the contact in an $^{85}$Rb atomic BEC using RF spectroscopy, investigates three-body interactions, and finds no measurable three-body contribution in the observed regime.

Contribution

It provides the first measurement of contact in a bosonic BEC and explores the role of three-body interactions, including locating an Efimov resonance.

Findings

Contact measured via RF spectroscopy in $^{85}$Rb BEC.

Located an Efimov resonance through loss measurements.

No detectable three-body physics contribution in the contact measurements.

Abstract

A powerful set of universal relations, centered on a quantity called the contact, connects the strength of short-range two-body correlations to the thermodynamics of a many-body system with delta-function interactions. We report on measurements of the contact, using RF spectroscopy, for an $^{85}$Rb atomic Bose-Einstein condensate (BEC). For bosons, the fact that contact spectroscopy can be used to probe the gas on short timescales is useful given the decreasing stability of BECs with increasing interactions. A complication is the added possibility, for bosons, of three-body interactions. In investigating this issue, we have located an Efimov resonance for $^{85}$Rb atoms with loss measurements and thus determined the three-body interaction parameter. In our contact spectroscopy, in a region of observable beyond-mean-field effects, we find no measurable contribution from three-body physics.