Bose-Einstein condensates of polar molecules: anisotropic interactions = anisotropic mass

TL;DR

This paper develops a rigorous theoretical framework for Bose-Einstein condensates of polar molecules, revealing that anisotropic dipolar interactions significantly modify the effective mass, especially along the polarizing field, with potential reductions up to 1000 times.

Contribution

It introduces a pseudo-potential approach to derive a non-linear Schrödinger equation for dipolar BECs, showing anisotropic mass effects not previously accounted for.

Findings

Effective mass is reduced by 10% in alkali-metal atom BECs.

Polar molecule BECs can have their mass reduced by a factor of 1000.

Anisotropic interactions primarily affect motion along the polarizing field.

Abstract

So far the theory of Bose-Einstein condensates (BEC) of polar molecules was based on an ad hoc generalization of equations for spherical atoms. Here I adopt a rigorous pseudo-potential approach to low-energy dipolar interactions and derive a non-linear mean-field Schrodinger equation for a harmonically-trapped condensate. I show that, effectively, the dipolar interactions alter molecular mass. The resulting effective mass is anisotropic: to the leading order the mass is altered only for the motion along the polarizing field. For a typical BEC of spin-polarized magnetically-interacting alkali-metal atoms the effective atomic mass is reduced by 10% from its bare value. For a BEC of polar molecules the mass may be reduced by a factor of a 1,000.