Hydrodynamics of Spatially Ordered Superfluids

TL;DR

This paper derives hydrodynamic equations for 2D supersolid and superhexatic phases, revealing their ability to sustain third-sound modes and additional defect-related modes in the supersolid phase.

Contribution

It provides a theoretical framework for understanding hydrodynamics in supersolid and superhexatic phases of 2D Bose fluids, including defect dynamics.

Findings

Both phases support third-sound modes.

Supersolid phase exhibits additional defect-related modes.

Normal fluid component is assumed to be substrate-bound.

Abstract

We derive the hydrodynamic equations for the supersolid and superhexatic phases of a neutral two-dimensional Bose fluid. We find, assuming that the normal part of the fluid is clamped to an underlying substrate, that both phases can sustain third-sound modes and that in the supersolid phase there are additional modes due to the superfluid motion of point defects (vacancies and interstitials).