Kelvin-Helmholtz instability in two-component Bose gases on a lattice

TL;DR

This paper investigates how lattice effects, broken symmetry, and strong correlations influence the Kelvin-Helmholtz instability in two-component Bose gases, revealing stabilization mechanisms and vortex formation near a Mott transition.

Contribution

It introduces a combined theoretical approach to study the instability on a lattice, highlighting the qualitative effects of discreteness, symmetry breaking, and correlations.

Findings

Discreteness stabilizes low flow velocities.

Broken symmetry affects dependence on absolute velocities.

Strong correlations inhibit turbulence, favoring vortex formation.

Abstract

We explore the stability of the interface between two phase-separated Bose gases in relative motion on a lattice. Gross-Pitaevskii-Bogoliubov theory and the Gutzwiller ansatz are employed to study the short- and long-time stability properties. The underlying lattice introduces effects of discreteness, broken spatial symmetry, and strong correlations, all three of which are seen to have considerable qualitative effects on the Kelvin-Helmholtz instability. Discreteness is found to stabilize low flow velocities, because of the finite energy associated with displacing the interface. Broken spatial symmetry introduces a dependence not only on the relative flow velocity, but on the absolute velocities. Strong correlations close to a Mott transition will stop the Kelvin-Helmholtz instability from affecting the bulk density and creating turbulence; instead, the instability will excite vortices with Mott-insulator filled cores.