Capillary-wave dynamics and interface structure modulation in binary Bose-Einstein condensate mixtures

Abstract

The localized low-energy interfacial excitations, or Nambu-Goldstone modes, of phase-segregated binary mixtures of Bose-Einstein condensates are investigated analytically by means of a doubleparabola approximation (DPA) to the Lagrangian density in Gross-Pitaevskii theory for a system in a uniform potential. Within this model analytic expressions are obtained for the excitations underlying capillary waves or "ripplons" for arbitrary strength K (> 1) of the phase segregation.The dispersion relation ω ∝ k 3/2 is derived directly from the Bogoliubov-de Gennes equations in limit that the wavelength 2π/k is much larger than the healing length ξ. The proportionality constant in the dispersion relation provides the static interfacial tension. A correction term in ω(k) of order k 5/2 is calculated analytically, entailing a finite-wavelength correction factor (1 +). This prediction may be tested experimentally using (quasi-)uniform optical-box traps. Explicit expressions are obtained for the structural deformation of the interface due to the passing of the capillary wave. It is found that the amplitude of the wave is enhanced by an amount that is quadratic in the ratio of the phase velocity ω/k to the sound velocity c. For generic asymmetric mixtures consisting of condensates with unequal healing lengths an additional modulation is predicted of the common value of the condensate densities at the interface.

Interface potential and line tension for Bose-Einstein condensate mixtures near a hard wall

“…Additionally, the experimental probing of an ultracold-gas interface was recently shown for a Bose-Fermi system [24] while multiple studies stipulate the important role of interface physics in explaining equilibrium configurations of current-day experimental situations [25][26][27][28]. Interface statics [29] and especially interface dynamics of multi-component condensates gained substantial recent attention [30][31][32][33].…”

Instabilities of vortex-ring-bright soliton in trapped binary 3D Bose-Einstein condensates

“…Indeed, such multi-component settings have offered an ideal framework for the exploration of ideas of phase separation [18][19][20][21], but also for the manifestation of a wide range of fluid-like instabilities. The latter include, among others, the Rayleigh-Taylor instability [22][23][24], the Kelvin-Helmholtz instability [25][26][27], the capillary [28,29] and Richtmyer-Meshkov [30] instabilities, as well as the countersuperflow [31][32][33][34], but also the Rosensweig [35] instabilities. This wealth of findings clearly illustrates the fact that multi-component systems may possess a significant additional wealth of features, in comparison with the simpler single-component ones.…”

Interface properties in three-component Bose-Einstein condensates

“…When the two components are immiscible, phase separation occurs and interfaces are formed [5][6][7][8]. The static and dynamic properties of such interfaces have been investigated theoretically [9][10][11][12][13][14][15][16][17][18][19][20][21]. The interfacial tension coefficients for an immiscible two-component BEC were obtained analytically and numerically in Refs.…”