Mean-field and stability analysis of two-dimensional flowing soft-core bosons modeling a supersolid

TL;DR

This paper analyzes the stability of flowing states in a two-dimensional soft-core boson model of supersolids using mean-field theory and excitation spectra, revealing conditions for metastable superflow in different phases.

Contribution

It provides a stability phase diagram for superflow states in soft-core boson supersolids, a topic previously lacking detailed analysis.

Findings

Excitation spectra differ across superfluid, supersolid, and stripe phases.

Metastable superflow regions are mapped in the phase diagram.

Stability depends on phase-specific excitation characteristics.

Abstract

The soft-core boson system is one of the simplest models of supersolids, which have both off-diagonal long-range order (Bose-Einstein condensation) and diagonal long-range order (crystalline order). Although this model has been studied from various points of view, studies of the stability of current-flowing states are lacking. Solving the Gross-Pitaevskii and Bogoliubov equations, we obtain excitation spectra in superfluid, supersolid, and stripe phases. On the basis of the results of the excitation spectra, we present a stability phase diagram that shows the region of the metastable superflow states for each phase.