A magic tilt angle for stabilizing two-dimensional solitons by dipole-dipole interactions

TL;DR

This study demonstrates that dipole-dipole interactions at a specific tilt angle can stabilize two-dimensional solitons in dipolar Bose-Einstein condensates, which are otherwise unstable due to attractive contact interactions.

Contribution

It introduces the concept of a 'magic tilt angle' where dipole-dipole interactions stabilize 2D solitons in dipolar BECs, expanding understanding of soliton stability mechanisms.

Findings

Unstable Townes solitons can be stabilized by DDI at certain angles.

The critical angle for stability is close to the magic angle, cf3s(1/b3).

Dipole-dipole interactions can create stable higher-dimensional BEC solitons.

Abstract

In the framework of the Gross-Pitaevskii equation, we study the formation and stability of effectively two-dimensional solitons in dipolar Bose-Einstein condensates (BECs), with dipole moments polarized at an arbitrary angle $\theta$ relative to the direction normal to the system's plane. Using numerical methods and the variational approximation, we demonstrate that unstable Townes solitons, created by the contact attractive interaction, may be completely stabilized (with an anisotropic shape) by the dipole-dipole interaction (DDI), in interval $\theta ^{\text{cr}}<\theta \leq \pi /2$. The stability boundary, $\theta ^{\text{cr}}$, weakly depends on the relative strength of DDI, remaining close to the "magic angle", $\theta_{m}=\arccos \left( 1/\sqrt{3}\right) $. The results suggest that DDIs provide a generic mechanism for the creation of stable BEC\ solitons in higher dimensions.