Fluctuation- and interaction-induced instability of dark solitons in single and binary condensates

Roy, Arko; Angom, D.

doi:10.1103/physreva.90.023612

Cited by 14 publications

(14 citation statements)

References 61 publications

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“…where the oscillation frequency Eq. (16b) corresponds to the zero-energy mode, sometimes defined in the literature as a Goldstone mode [29,35]. This mode breaks translational symmetry with no energy cost.…”

Section: Normal Modesmentioning

confidence: 99%

Dynamics of dark-bright vector solitons in Bose-Einstein condensates

Alotaibi

Carr

2017

Phys. Rev. A

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We analyze the dynamics of two-component vector solitons, namely bright-in-dark solitons, via the variational approximation in Bose-Einstein condensates. The system is described by a vector nonlinear Schrödinger equation appropriate to multi-component Bose-Einstein condensates (BECs). The variational approximation is based on hyperbolic secant (hyperbolic tangent) for the bright (dark) component, which leads to a system of coupled ordinary differential equations for the evolution of the ansatz parameters. We obtain the oscillation dynamics of two-component dark-bright vector solitons. Analytical calculations are performed for same-width components in the vector soliton and numerical calculations extend the results to arbitrary widths. We calculate the binding energy of the system and find it proportional to the intercomponent coupling interaction, and numerically demonstrate the break up or unbinding of a dark-bright soliton. Our calculations explore observable eigenmodes, namely the internal oscillation eigenmode and the Goldstone eigenmode. We find analytically that the density of the bright component is required to be less than the density of the dark component in order to find the internal oscillation eigenmode of the vector soliton and support the existence of the dark-bright soliton. This outcome is confirmed by numerical results. Numerically, we find that the oscillation frequency is amplitude independent. For dark-bright vector solitons in 87 Rb we find that the oscillation frequency range is 90 to 405 Hz, and therefore observable in multi-component BEC experiments.arXiv:1607.00108v2 [cond-mat.quant-gas]

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Section: Normal Modesmentioning

confidence: 99%

Dynamics of dark-bright vector solitons in Bose-Einstein condensates

Alotaibi

Carr

2017

Phys. Rev. A

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“…In this Letter we address this issue by using Hartree-Fock-Bogoliubov theory with Popov approximation (HFB-Popov) [19] to account for the thermal fluctuations. It is a gapless formalism satisfying Hugenholtz-Pines theorem [20] and can be employed to compute the energy eigenspectra of the quasiparticle excitations of the condensates.The method has been validated extensively in single species BEC, and we have used it in our recent works to examine the effect of quantum fluctuations in TBECs [21]. In the present work, we systematically study the role of thermal fluctuations in the phenomenon of phase-separation in trapped TBECs.…”

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confidence: 99%

Thermal suppression of phase separation in condensate mixtures

Roy

Angom

2015

Phys. Rev. A

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We examine the role of thermal fluctuations in binary condensate mixtures of dilute atomic gases. In particular, we use Hartree-Fock-Bogoliubov with Popov approximation to probe the impact of non-condensate atoms to the phenomenon of phase-separation in two-component Bose-Einstein condensates. We demonstrate that, in comparison to T = 0, there is a suppression in the phase-separation of the binary condensates at T = 0. This arises from the interaction of the condensate atoms with the thermal cloud. We also show that, when T = 0 it is possible to distinguish the phase-separated case from miscible from the trends in the correlation function. However, this is not the case at T = 0. [15], is that the intra-(U 11 , U 22 ) and inter-species interaction (U 12 ) strengths, must satisfy the inequality U 2 12 > U 11 U 22 . However, experiments are conducted at finite temperatures, and therefore, deviations from the criterion is to be expected. Theoretical studies on effects of thermal cloud on phase-separation have been carried out for homogeneous binary Bose gases using HartreeFock theory [16] and large-N approximation [17]. Phaseseparation of trapped binary mixtures at finite temperature has also been examined using local-density approximation [18]. In this Letter we address this issue by using Hartree-FockBogoliubov theory with Popov approximation (HFB-Popov) [19] to account for the thermal fluctuations. It is a gapless formalism satisfying Hugenholtz-Pines theorem [20] and can be employed to compute the energy eigenspectra of the quasiparticle excitations of the condensates.The method has been validated extensively in single species BEC, and we have used it in our recent works to examine the effect of quantum fluctuations in TBECs [21]. In the present work, we systematically study the role of thermal fluctuations in the phenomenon of phase-separation in trapped TBECs. Our studies reveal that at T = 0, the constituent species in the TBEC undergo phase-separation at a higher U 12 than the value predicted based on the TF-approximation at T = 0. Consistent with experimental observations of dual species condensate of 87 Rb and 133 Cs [7], our theoretical investigations show that even when the phase-separation condition is met, there is a sizable overlap between the two species. We attribute this to the presence of the thermal cloud, which have profound affects on the miscibility-immiscibility transition. At T = 0, the TBECs are coherent throughout the spatial extent of the condensate, however, when T = 0 coherence decays and is reflected in the correlation function. This implies that at T = 0, the miscible or immiscible phases are indistinguishable from the trends in the correlation function. But, for T = 0 the miscible-immiscible transition and the associated changes in the density profiles have a characteristic signature in the form of the correlation functions. There is a smooth cross-over between the correlations functions when the transition occurs. Interspecies Feshbach resonances of ultracold bosons have been exper...

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“…This breaks the z-parity symmetry of the system, and the zero-energy mode then starts to regain energy after phase-separation [15]. Detailed discussions on Goldstone modes and bifurcations in TBECs with or without soliton are discussed in our previous works [17,19].…”

Section: Third Goldstone Mode Inmentioning

confidence: 93%

Evolution of Goldstone mode in binary condensate mixtures

Roy

Gautam

Angom

2015

Eur. Phys. J. Spec. Top.

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Abstract. We show that the third Goldstone mode in the two-species condensate mixtures, which emerges at phase-separation, gets hardened when the confining potentials have separated trap centers. The sandwich type condensate density profiles, in this case, acquire a sideby-side density profile configuration. We use Hartree-Fock-Bogoliubov theory with Popov approximation to examine the mode evolution and density profiles for these phase transitions at T = 0.

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Fluctuation- and interaction-induced instability of dark solitons in single and binary condensates

Cited by 14 publications

References 61 publications

Dynamics of dark-bright vector solitons in Bose-Einstein condensates

Dynamics of dark-bright vector solitons in Bose-Einstein condensates

Thermal suppression of phase separation in condensate mixtures

Evolution of Goldstone mode in binary condensate mixtures

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