Instability crossover of helical shear flow in segregated Bose-Einstein condensates

TL;DR

This paper investigates the stability of helical shear flows in phase-separated two-component Bose-Einstein condensates, revealing a crossover between vortex sheet and core-flow regimes with competing instabilities.

Contribution

It provides a theoretical analysis of the instability crossover in helical shear flows, distinguishing two regimes and identifying dominant instability modes in each.

Findings

Identification of two distinct regimes of helical shear flow stability.

Analysis of ripple, Kelvin, and varicose modes in different regimes.

Discovery of competition among instabilities in the crossover regime.

Abstract

We theoretically study the instability of helical shear flows, in which one fluid component flows along the vortex core of the other, in phase-separated two-component Bose-Einstein condensates at zero temperature. The helical shear flows are hydrodynamically classified into two regimes: (1) a helical vortex sheet, where the vorticity is localized on the cylindrical interface and the stability is described by an effective theory for ripple modes, and (2) a core-flow vortex with the vorticity distributed in the vicinity of the vortex core, where the instability phenomena are dominated only by the vortex-characteristic modes: Kelvin and varicose modes. The helical shear-flow instability shows remarkable competition among different types of instabilities in the crossover regime between the two regimes.