Collective modes in multicomponent condensates with anisotropy

Pal, Sukla; Roy, Arko; Angom, D.

doi:10.1088/1361-6455/aab541

Cited by 7 publications

(6 citation statements)

References 63 publications

(93 reference statements)

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“…Though the eigenvalues are printed in hfb2d2s.out, for other detailed computations like the mode evolution as a function of anisotropy and interaction parameters, the energy eigenvalues are also stored in the output file eigenvalue.out. Such data is useful in studies like our previous works [16,17], where we have shown the mode evolution as a function of various parameters using these package. It is to be mentioned that, the energy eigen values, chemical potentials and total energy of the system, calculated in this package are in units of ω x .…”

Section: Output Datamentioning

confidence: 94%

“…To examine the effect of anisotropy in the trapping parameter one can consider AL < 1 (corresponding to ω y ω x , the TBEC is elongated along y axis) or AL > 1 (corresponding to ω x ω y , the TBEC is elongated along x axis). In our recent work [17], we have considered the effect of anisotropy in 85 Rb -87 Rb TBEC at zero temperature for AL > 1. To make the system quasi-2D a large value of anisotropy parameter along axial direction LAMBDA = 12.5 is chosen so that the condition µ ω z is satisfied.…”

Section: Initializementioning

confidence: 99%

“…These are important in the stabilization of quantum droplets in binary BEC mixtures [12][13][14][15]. In our recent works [16,17] we have investigated the elementary excitations in radially symmetric and and anisotropic TBECs using the present version of FACt. However, the main strength of HFB-Popov approximation is in encapsulating properties of trapped BEC at finite temperatures, which is more realistic and experimentally relevant.…”

Section: Introductionmentioning

confidence: 99%

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FACt: FORTRAN toolbox for calculating fluctuations in atomic condensates

Roy

Pal

Gautam

et al. 2020

Computer Physics Communications

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We develop a FORTRAN code to compute fluctuations in atomic condensates (FACt) by solving the Bogoliubov-de Gennes (BdG) equations for two component Bose-Einstein condensate (TBEC) in quasi two dimensions. The BdG equations are recast as matrix equations and solved self consistently. The code is suitable for handling quantum fluctuations as well as thermal fluctuations at temperatures below the critical point of Bose-Einstein condensation. The code is versatile, and the ground state density profile and low energy excitation modes obtained from the code can be easily adapted to compute different properties of TBECs -ground state energy, overlap integral, quasi particle amplitudes of BdG spectrum, dispersion relation and structure factor and other related experimental observables.External routines/libraries: ARPACK Subprograms used: Journal reference of previous version:* Nature of problem: Compute the ground state density profile, ground state energy and chemical potential for individual species, evaluate the quasiparticle mode energies and corresponding amplitudes which can capture the transformation of the modes against the change of the parameters (intraspecies interaction, interspecies interaction, anisotropy parameter etc.) using Hartree-Fock Bogoliubov theory with the Popov approximation Calculate the overlap integral, dispersion relation and structure factor. Solution method: In the first step, the pair of coupled Gross-Pitaevskii (GP) equations are solved using split step Crank-Nicolson method to compute the condensate density.To solve BdG equations, as a basic input the first N b harmonic oscillator eigenstates are chosen as a basis to generate the BdG matrix with dimension of 4(N b + 1)(N b + 1) × 4(N b + 1)(N b + 1). Since the matrix size rapidly increases with N b , ARPACK routines are used to diagonalise the BdG matrix efficiently. To compute the fluctuation and noncondensate density, a set of the low energy quasiparticle amplitudes above a threshold value of the Bose factor are considered. The equations are then solved iteratively till the condensate, and non-condensate densities converge to predefined accuracies. To accelerate the convergence we use the method of successive under-relaxation (SUR).Restrictions: For a large system size, if the harmonic oscillator basis size is also taken to be large, the dimension of the BDG matrix becomes huge. It may take several days to compute the low energy modes at finite temperature and this package may be computationally expensive.Additional comments:After successful computation of this package, one should obtain the equilibrium density profiles for TBEC, low energy Bogoliubov modes and the corresponding quasiparticle amplitudes. In addition, one can calculate the dispersion relation, structure factor, overlap integral, correlation function, etc. using this package with minimal modifications. In the theory section of the manuscript, we have provided the expressions to compute the above quantities numerically.Running time: ∼ 10 minutes for the sample case. For ...

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Section: Output Datamentioning

confidence: 94%

Section: Initializementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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FACt: FORTRAN toolbox for calculating fluctuations in atomic condensates

Roy

Pal

Gautam

et al. 2020

Computer Physics Communications

Self Cite

View full text Add to dashboard Cite

show abstract

“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Van Schaeybroeck,

Navez,

Indekeu

2022

Preprint

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Within Gross-Pitaevskii (GP) theory we derive the interface potential V (ℓ) which describes the interaction between the interface separating two demixed Bose-condensed gases and an optical hard wall at a distance ℓ. Previous work revealed that this interaction gives rise to extraordinary wetting and prewetting phenomena. Calculations that explore non-equilibrium properties by using ℓ as a constraint provide a thorough explanation for this behavior. We find that at bulk two-phase coexistence, V (ℓ) for both complete wetting and partial wetting is monotonic with exponential decay. Remarkably, at the first-order wetting phase transition, V (ℓ) is independent of ℓ. This anomaly explains the infinite continuous degeneracy of the grand potential reported earlier. As a physical application, using V (ℓ) we study the three-phase contact line where the interface meets the wall under a contact angle θ. Employing an interface displacement model we calculate the structure of this inhomogeneity and its line tension τ . Contrary to what happens at a usual first-order wetting transition in systems with short-range forces, τ does not approach a nonzero positive constant for θ → 0, but instead approaches zero (from below) in the manner τ ∝ −θ as would be expected for a critical wetting transition. This hybrid character of τ is a consequence of the absence of a barrier in V (ℓ) at wetting. For a typical V (ℓ) = S exp(−ℓ/ξ), with S the spreading coefficient, we conjecture that τ = −2 (1 − ln 2) γ ξ sin θ is exact within GP theory, with γ the interfacial tension and 0 ≤ θ ≤ π.

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“…It was found that the Rabi coupling stabilizes the superfluid phase in coupled BECs in optical lattices [32]. A variety of collective modes, namely, Nambu-Goldstone, slosh, bifurcation modes were studied in the trapped two-component quasitwo-dimensional (quasi-2D) BECs [33,34].…”

Section: Introductionmentioning

confidence: 99%

Effect of Rashba spin-orbit and Rabi couplings on the excitation spectrum of binary Bose-Einstein condensates

Ravisankar,

Fabrelli,

Gammal

et al. 2021

Preprint

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We present the collective excitation spectrum analysis of binary Bose-Einstein condensates (BECs) with spin-orbit (SO) and Rabi couplings in a quasi-two-dimensional system. In particular, we investigate the role of SO and Rabi coupling strengths in determining the dynamical stability of the coupled BECs using Bogoliubov-de Gennes (BdG) theory. Using the eigenergy of BdG spectrum, we confirm the existence of phonon, roton, and maxon modes with weak repulsive intra-and interspecies contact interactions. The depth of the minimum corresponding to the roton mode depends strongly on the coupling strength. We find that the increase of the SO coupling leads to instability, while the increase in the Rabi coupling stabilizes the system. Also the eigenvectors of BdG spectrum indicates the presence of density like mode in the stable regime and spin like modes in unstable regimes. A phase diagram demonstrating the stability regime in the plane of SO and Rabi coupling strengths is obtained. Finally, we complement the observation of the excitation spectrum with the direct numerical simulation results of coupled Gross-Pitaevskii equations.

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Collective modes in multicomponent condensates with anisotropy

Cited by 7 publications

References 63 publications

FACt: FORTRAN toolbox for calculating fluctuations in atomic condensates

FACt: FORTRAN toolbox for calculating fluctuations in atomic condensates

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

Effect of Rashba spin-orbit and Rabi couplings on the excitation spectrum of binary Bose-Einstein condensates

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