Effect of interactions in the interference pattern of Bose Einstein condensates

TL;DR

This paper investigates how interactions affect the interference patterns of expanding Bose-Einstein condensates, revealing that mutual interactions only modify the phase locally where condensates overlap.

Contribution

It provides combined experimental and theoretical evidence showing that interactions cause local phase modifications during condensate overlap, challenging previous assumptions.

Findings

Interactions produce local phase modifications only during wavepacket overlap

Experimental and theoretical results agree on the localized effect of interactions

Challenges the assumption of a uniform phase shift due to interactions

Abstract

Understanding the effect of interactions in the phase evolution of expanding atomic Bose Einstein condensates is fundamental to describe the basic phenomenon of matter wave interference. Many theoretical and experimental works tackled this problem, always with the implicit assumption that the mutual interaction between two expanding condensates rigidly modifies the phase evolution through an effective force. In this paper, we present a combined experimental and theoretical investigation of the interference profile of expanding $^{87}$Rb condensates, with a specific focus on the effect of interactions. We come to the different conclusion that the mutual interaction produces local modifications of the condensate phase only in the region where the wavepackets overlap.