Thermal and quantum fluctuations of confined Bose–Einstein condensate beyond the Bogoliubov approximation

Nakamura, Yusuke; Kawaguchi, T.; Torii, Yoshio; Yamanaka, Yoshiya

doi:10.1016/j.aop.2016.12.020

Cited by 4 publications

(3 citation statements)

References 28 publications

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“…As was previously discussed in Ref. [30,31], the quantum fluctuations of the zero mode cannot be suppressed in a trapped system, but should be properly incorporated in any analysis. The problem of the renormalization condition including the zero mode remains open.…”

Section: Discussionmentioning

confidence: 97%

Self-energy renormalization for inhomogeneous nonequilibrium systems and field expansion via complete set of time-dependent wavefunctions

Kuwahara

Nakamura

Yamanaka

2018

Int. J. Mod. Phys. B

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The way to determine the renormalized energy of inhomogeneous systems of a quantum field under an external potential is established for both equilibrium and nonequilibrium scenarios based on Thermo Field Dynamics. The key step is to find an extension of the on-shell concept valid in homogeneous case. In the nonequilibrium case, we expand the field operator by time-dependent wave functions that are solutions of the appropriately chosen differential equation, synchronizing with temporal change of thermal situation, and the quantum transport equation is derived from the renormalization procedure. Through numerical calculations of a triple-well model with a reservoir, we show that the number distribution and the time-dependent wave functions are relaxed consistently to the correct equilibrium forms at the long-term limit. a present address: Nagano Prefectural Kiso Seiho High School, Nagano 397-8571, Japan

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Section: Discussionmentioning

confidence: 97%

Self-energy renormalization for inhomogeneous nonequilibrium systems and field expansion via complete set of time-dependent wavefunctions

Kuwahara

Nakamura

Yamanaka

2018

Int. J. Mod. Phys. B

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“…For another direction of research, we will further develop the present method to look into zero-mode physics [101][102][103], few-body physics, self-localization, and so on.…”

Section: Discussionmentioning

confidence: 99%

Bose polaron in spherical trap potentials: Spatial structure and quantum depletion

Takahashi¹,

Imai

Nakano

et al. 2019

Phys. Rev. A

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We investigate how the presence of a localized impurity in a Bose-Einstein condensate of trapped cold atoms that interact with each other weakly and repulsively affects the profile of the condensed and excited components at zero temperature. By solving the Gross-Pitaevskii and Bogoliubovde Gennes equations, we find that an impurity-boson contact attraction (repulsion) causes both components to change in spatial structure in such a way as to be enhanced (suppressed) around the impurity, while slightly declining (growing) in a far region from the impurity. Such behavior of the quantum depletion of the condensate can be understood by decomposing the impurity-induced change in the profile of the excited component with respect to the radial and azimuthal quantum number. A significant role of the centrifugal potential and the "hole" excitation level is thus clarified.

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“…In most of recent experimental researches, the Bose polarons are realized in the system of the repulsive boson-boson interactions where the medium-bosons form a superfluid BEC. In order to analyze such cases, we need Bogoliubov-de-Gennes-type approaches [84][85][86][87][88][89] beyond the Bogoliubov approximation. Such extensions of the present approach for the trapped polaron including the boson-boson interactions should give more detailed polaron's structures such as a local depletion of BEC around impurity as well as the excitation spectra of the bosonic sector.…”

Section: Discussionmentioning

confidence: 99%

Bose polaron in spherically symmetric trap potentials: Ground states with zero and lower angular momenta

2019

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Single-atomic impurities immersed in a dilute Bose gas in the spherically symmetric harmonic trap potentials are studied at zero temperature. In order to find the ground state of the polarons, we present a conditional variational method with fixed expectation values of the total angular momentum operators,Ĵ 2 andĴ z , of the system, using a cranking gauge-transformation for bosons to move them in the frame co-rotating with the impurity. In the formulation, the expectation value Ĵ2 is shown to be shared in impurity and bosons, but the value Ĵ z is carried by the impurity due to the rotational symmetry. We also analyze the ground-state properties numerically obtained in this variational method for the system of the attractive impurity-boson interaction, and find that excited boson distributions around the impurity overlap largely with impurity's wave function in their quantum-number spaces and also in the real space because of the attractive interaction employed. * Electronic address: b17m6c17m@kochi-u.ac.jp

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Thermal and quantum fluctuations of confined Bose–Einstein condensate beyond the Bogoliubov approximation

Cited by 4 publications

References 28 publications

Self-energy renormalization for inhomogeneous nonequilibrium systems and field expansion via complete set of time-dependent wavefunctions

Self-energy renormalization for inhomogeneous nonequilibrium systems and field expansion via complete set of time-dependent wavefunctions

Bose polaron in spherical trap potentials: Spatial structure and quantum depletion

Bose polaron in spherically symmetric trap potentials: Ground states with zero and lower angular momenta

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