Dipolar Bose Superstripes

TL;DR

This study investigates the superfluid properties of a 2D dipolar Bose gas with arbitrary polarization angles, revealing persistent Bose condensation and anisotropic superfluidity within the stripe phase using advanced quantum Monte Carlo methods.

Contribution

It provides the first detailed analysis of superfluidity and Bose condensation in the stripe phase of dipolar bosons with arbitrary polarization angles.

Findings

Superfluid fraction along stripes is close to 1.

Superfluid fraction perpendicular to stripes is small but non-zero.

Bose condensate persists despite oscillatory density correlations.

Abstract

We study the superfluid properties of a system of fully polarized dipolar bosons moving in the $xy$ plane. We focus on the general case where the polarization field forms an arbitrary angle $\alpha$ with respect to the $z$ axis, while the system is still stable. We use the diffusion Monte Carlo and the path integral ground state methods to evaluate the one-body density matrix and the superfluid fractions in the region of the phase diagram where the system forms stripes. Despite its oscillatory behavior, the presence of a finite large-distance asymptotic value in the $s$-wave component of the one-body density matrix indicates the existence of a Bose condensate. The superfluid fraction along the stripes direction is always close to 1, while in the $y$ direction decreases to a small value that is nevertheless different from zero. These two facts confirms that the stripe phase of the dipolar Bose gas in 2D is superfluid.