Dipolar Bose Superstripes

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.