Energy Of Condensate Research Articles

Controlling the Spatial Profile and Energy Landscape of Organic Polariton Condensates in Double-Dye Cavities.

The development of high-speed, all-optical polariton logic devices underlies emerging unconventional computing technologies and relies on advancing techniques to reversibly manipulate the spatial extent and energy of polartion condensates. We investigate active spatial control of polariton condensates independent of the polariton, gain-inducing excitation profile. This is achieved by introducing an extra intracavity semiconductor layer, nonresonant to the cavity mode. Partial saturation of the optical absorption in the uncoupled layer enables the ultrafast modulation of the effective refractive index and, through excited-state absorption, the polariton dissipation. Utilizing an intricate interplay of these mechanisms, we demonstrate control over the spatial profile, density, and energy of a polariton condensate at room temperature.

Few Excited State Energies and Chemical Potential Energy of 87Rb Condensate by Many-Body Approach

We consider experimental 87Rb condensate which is trapped by harmonic plus quartic trap [V(r) = ½mω2r2 + λr4]. Keeping similarity with experiments, the anharmonic parameter (λ) is considered as a controllable parameter. The excited state energies of stable Bose-Einstein condensate are strongly influenced by the presence of an anharmonic term, even when the interatomic interaction is repulsive. The necessary dependencies of excited state energies of the trapped condensate on λ are discussed in detail. In addition, the variation of chemical potential energy as a function of λ is also investigated to explore the role of interaction. The many-particle Schrödinger equation is solved by the potential harmonic expansion method, where all possible two-body correlations are considered by utilizing the correlated two-body basis function. Specifically, we present a clear physical explanation of excited state energies and chemical potential energy of the experimental repulsive condensate confined by the anharmonic trap.

Interplay of nonreciprocity and nonlinearity on mean-field energy and dynamics of a Bose-Einstein condensate in a double-well potential

We investigate the mean-field energy spectrum and dynamics in a Bose-Einstein condensate in a double-well potential with non-Hermiticity from the nonreciprocal hopping, and show that the interplay of nonreciprocity and nonlinearity leads to exotic properties. Under the two-mode and mean-field approximations, the nonreciprocal generalization of the nonlinear Schr\"{o}dinger equation and Bloch equations of motion for this system are obtained. We analyze the PT phase diagram and the dynamical stability of fixed points. The reentrance of PT-symmetric phase and the reformation of stable fixed points with increasing the nonreciprocity parameter are found. Besides, we uncover a linear self-trapping effect induced by the nonreciprocity. In the nonlinear case, the self-trapping oscillation is enhanced by the nonreciprocity and then collapses in the PT-broken phase, and can finally be recovered in the reentrant PT-symmetric phase.

Beneficial use of thermal secondary energy resources in the rectification cycle at ethylene glycol production unit

Efficient use of secondary energy resources at the oil and gas chemical industry plants affects the final cost of the products. One of the energy-intensive cycles in organic production is the rectification process, which is accompanied by a high yield of thermal secondary energy resources. The energy intensity of the process is associated with the need to evaporate one of the mixture components while consuming at least the vapourization heat. There is the option of organization of technical solution of useful use of thermal energy of condensate after the rectification cycle for the purpose of heating the reaction mixture at the article.

Preheating after Higgs inflation: Self-resonance and gauge boson production

We perform an extensive analysis of linear fluctuations during preheating in Higgs inflation in the Einstein frame, where the fields are minimally coupled to gravity, but the field-space metric is nontrivial. The self-resonance of the Higgs and the Higgsed gauge bosons are governed by effective masses that scale differently with the nonminimal couplings and evolve differently in time. Coupled metric perturbations enhance Higgs self-resonance and make it possible for Higgs inflation to preheat solely through this channel. For $\xi\gtrsim 100$ the total energy of the Higgs-inflaton condensate can be transferred to Higgs particles within $3$ $e$-folds after the end of inflation. For smaller values of the nonminimal coupling preheating takes longer, completely shutting off at around $\xi\simeq 30$. The production of gauge bosons is dominated by the gauge boson mass and the field space curvature. For large values of the nonminimal coupling $\xi \gtrsim 1000$, it is possible for the Higgs condensate to transfer the entirety of its energy into gauge fields within one oscillation. For smaller values of the nonminimal coupling gauge bosons decay very quickly into fermions, thereby shutting off Bose enhancement. Estimates of non-Abelian interactions indicate that they will not suppress preheating into gauge bosons for $\xi \gtrsim 1000$.

On the Position-Dependent Effective Mass in Bose Condensates of Photons and Polaritons in an Optical Microcavity Trap

The effect of the particle position-dependent effective mass on the behavior of quasi-two-dimensional photon and exciton-polariton condensates in a parabolic trap in a semiconductor optical microcavity is investigated. It is demonstrated that the correct inclusion of the coordinate dependence of the effective mass in the kinetic-energy operator modifies the effective confining potential for the particles. Corrections to the energy and wavefunction of the photon Bose condensate are derived. For exciton-polaritons, it is shown that the choice of specific mirror geometry can lead to the change from repulsive to attractive particle–particle interaction.

Self-shedding and sweeping of condensate on composite nano-surface under external force field: enhancement mechanism for dropwise and filmwise condensation modes

In this work, we propose the concept to use the hydrophilic or neutral surface for condensation heat transfer and to use the superhydrophobic surface for enhancement by self-shedding and sweeping of condensate. Molecular dynamics simulation results show that no matter the vapor condenses on the solid surface in dropwise or filmwise mode, the grown-up condensate self-sheds and falls off the superhydrophobic surface, sweeping the growing condensate on the condensing surface downstream. We characterize the dynamics of condensate that the continuous self-shedding and sweeping effectively remove the droplets from the solid surface in dropwise mode or thin the condensate film on the solid surface in filmwise mode, which significantly enhances the condensation heat transfer. We reveal that the mechanism for self-shedding is two-fold: (1) that the external force on condensate bulk defeats the adhesive force between the condensate and the solid surface triggers the self-shedding; (2) the release of the surface free energy of condensate promotes the self-shedding. We also reveal that the mechanism of heat transfer enhancement is essentially due to the timely suppression over the growing condensate bulk on the condensing surface through the self-shedding and sweeping. Finally, we discuss the possible applications.

Self-Gravitating Bose-Einstein Condensates and the Thomas-Fermi Approximation

Self-gravitating Bose-Einstein condensates (BEC) have been proposed in various astrophysical contexts, including Bose-stars and BEC dark matter halos. These systems are described by a combination of the Gross-Pitaevskii and Poisson equations (the GPP system). In the analysis of these hypothetical objects, the Thomas-Fermi (TF) approximation is widely used. This approximation is based on the assumption that in the presence of a large number of particles, the kinetic term in the Gross-Pitaevskii energy functional can be neglected, yet it is well known that this assumption is violated near the condensate surface. We also show that the total energy of the self-gravitating condensate in the TF-approximation is positive. The stability of a self-gravitating system is dependent on the total energy being negative. Therefore, the TF-approximation is ill suited to formulate initial conditions in numerical simulations. As an alternative, we offer an approximate solution of the full GPP system.

ON THE ORIGIN AND PHYSICS OF GAMMA FLARES IN CRAB NEBULA

We consider parametric generation of electrostatic waves in the magnetosphere of the pulsar PSR0531. The suggested mechanism allows us to convert the pulsar rotational energy into the energy of Langmuir waves. The maximum growth rate is achieved in the superluminal area, where the phase velocity of perturbations exceeds the speed of light. Therefore, electromagnetic waves do not damp on particles. Instead, they create plasmon condensate, which is carried out outside of the pulsar magnetosphere and reaches the Crab Nebula. It is shown that the transfer of the energy of the plasmon condensate from the light cylinder to the active region of the nebula happens practically without losses. Unlike the plasma of the magnetosphere, the one of the nebula contains ions, i.e., it may sustain modulation instability, that leads to the collapse of the Langmuir condensate. Langmuir wave collapse, in turn, leads to the acceleration of the distribution function particles. Furthermore, the processes that lead to self-trapping of the synchrotron radiation are discussed. The self-trapping results in the growth of the radiation intensity, which manifests itself observationally as a flare. The condition for the self-trapping onset is derived, showing that if the phenomenon takes place at 100 MeV, then it does not happen at lower (or higher) energies. This specific kind of higher-/lower-energy cutoff could explain why when we observe the flare at 100 MeV that no enhanced emission is observed at lower/higher energies!

Interfacial tension and wall energy of a Bose–Einstein condensate binary mixture: Triple-parabola approximation

Accurate and useful analytic approximations are developed for order parameter profiles and interfacial tensions of phase-separated binary mixtures of Bose–Einstein condensates. The pure condensates 1 and 2, each of which contains a particular species of atoms, feature healing lengths ξ1 and ξ2. The inter-atomic interactions are repulsive. In particular, the reduced inter-species repulsive interaction strength is K. A triple-parabola approximation (TPA) is proposed, to represent closely the energy density featured in Gross–Pitaevskii (GP) theory. This TPA allows us to define a model, which is a handy alternative to the full GP theory, while still possessing a simple analytic solution. The TPA offers a significant improvement over the recently introduced double-parabola approximation (DPA). In particular, a more accurate amplitude for the wall energy (of a single condensate) is derived and, importantly, a more correct expression for the interfacial tension (of two condensates) is obtained, which describes better its dependence on K in the strong segregation regime, while also the interface profiles undergo a qualitative improvement.

Big-bang nucleosynthesis and gamma-ray constraints on cosmic strings with a large Higgs condensate

We consider constraints on cosmic strings from their emission of Higgs particles, in the case that the strings have a Higgs condensate with amplitude of order the string mass scale, assuming that a fraction of the energy of condensate can be turned into radiation near cusps. The injection of energy by the decaying Higgs particles affects the light element abundances predicted by standard Big-Bang Nucleosynthesis (BBN), and also contributes to the Diffuse Gamma-Ray Background (DGRB) in the universe today. We examine the two main string scenarios (Nambu-Goto and field theory), and find that the primordial Helium abundance strongly constrains the string tension and the efficiency of the emission process in the NG scenario, while the strongest BBN constraint in the FT scenario comes from the Deuterium abundance. The Fermi-LAT measurement of the DGRB constrains the field theory scenario even more strongly than previously estimated from EGRET data, requiring that the product of the string tension {\mu} and Newton's constant G is bounded by G{\mu} < 2.7x10^{-11}{\beta}_{ft}^{-2}, where {\beta}_{ft}^2 is the fraction of the strings' energy going into Higgs particles.

Tuning the Energy of a Polariton Condensate via Bias-Controlled Rabi Splitting

An exciton polariton (a photon, electron, and a hole in a bound state, behaving as a boson) is a building block for a condensate that emits coherent light. On-chip manipulation of such condensates is an essential step toward polariton-based quantum information devices and lasers. In this work the energy of a polariton condensate in a high-finesse GaAs microcavity is tuned, bringing into reach polariton condensate devices that can be controlled by applied electrical bias.

Physical Evolution of Pressure-Driven Viral Infection

Physical Evolution of Pressure-Driven Viral Infection

Effective size and expansion energy of a Bose-Einstein condensate in a 3D non-cubic optical lattice

This work is devoted to study the temperature dependence of the effective size and expansion energy E_{x,z} of a Bose-Einstein condensate in a 3D non-cubic optical lattice. Correction due to the finite size, interatomic interaction and the deepness of the lattice potential are given simultaneously. The calculated results show that these two parameters increase with the lattice depth or the relative frequency at temperature less than the transition temperature, (T < T_o); yet it has little effect at temperatures higher than the transition temperature (T > T_o). Both the effective size and expansion energy follow a characteristic temperature dependence, i.e. , E \propto(T/T_0)^4 if T < T_0 and , E \propto (T/T_0) if T > T_0. For a 3D non cubic optical potential the effect of relative frequency is much more than the effect of the optical potential depth. Thus for a non-cubic optical potential one has to use the pure harmonically trapped boson gas as the zeroth order approximation in any perturbation or numerically treatment for this system.

Thermodynamic Analysis of the Effect of the Hierarchical Architecture of a Superhydrophobic Surface on a Condensed Drop State

Condensed drops usually display a Wenzel state on a superhydrophobic surface (SHS) only with microrough architecture, while Cassie drops easily appear on a surface with micro-nano hierarchical roughness. The mechanism of this is not very clear. It is important to understand how the hierarchical structure affects the states of condensation drops so that a good SHS can be designed to achieve the highly efficient dropwise condensation. In this study, the interface free energy (IFE) of a local condensate, which comes from the growth and combination of numerous initial condensation nuclei, was calculated during its shape changes from the early flat shape to a Wenzel or Cassie state. The final state of a condensed drop was determined by whether the IFE continuously decreased or a minimum value existed. The calculation results indicate that the condensation drops on the surface only with microroughness display a Wenzel state because the IFE curve of a condensed drop first decreases and then increases, existing at a minimum value corresponding to a Wenzel drop. On a surface with proper hierarchical roughness, however, the interface energy curve of a condensed drop will continuously decline until reaching a Cassie state. Therefore, a condensed drop on a hierarchical roughness surface can spontaneously change into a Cassie state. Besides, the states and apparent contact angles of condensed drops on a SHS with different structural parameters published in the literature were calculated and compared with experimental observations. The results show that the calculated condensed drop states are well-coordinated with experimental clarifications. We can conclude that micro-nano hierarchical roughness is the key structural factor for sustaining condensed drops in a Cassie state on a SHS.

Unitarity Schrödinger Equation and Ground State Properties of the Finite Trapped Superfluid Fermi Gases in a BCS-BEC Crossover

On the basis of quantum hydrodynamical equations we derive a unitarity Schrödinger equation of a finite trapped superfluid Fermi gas valid in the whole interaction regime from BCS superfluid to BEC. This equation is just the Ginzburg–Laudau-type equation for the fermionic Cooper pairs in the BCS side, the Gross–Pitaevskii-type equation for the bosonic dimers in the BEC side, and a unitarity equation for a strongly interacting Fermi superfluid in the unitarity limit. By taking a modified Gauss-like trial wave function, we solve the unitarity Schrödinger equation, calculate the energy, chemical potential, sizes and profiles of the ground-state condensate, and discuss the properties of the ground state in the entire BCS-BEC crossover regimes.

Phenomenological Equation of State and Density Profiles of Strongly Interacting Trapped Superfluid Fermi Gases with Arbitrary Atom Numbers

We present a phenomenological equation of state (EOS), derive a nonlinear quantum hydrodynamical equation and investigate the density profiles of a trapped superfluid Fermi gas with arbitrary number of particles in the BCS-BEC crossover regime. The asymptotic behavior of the EOS exactly matches with its expansions in three limiting regimes: BCS, unitarity and BEC. By using this EOS, the quantum hydrodynamical equation is beyond mean-field version, valid in all interacting regimes and used for the unitarity regime specially. We take a Fetter-like trial wave function in generalized Thomas-Fermi approximation, solve the hydrodynamical equation and calculate the energy, chemical potential, sizes and profiles of the ground-state condensate in the BCS-BEC crossover regime. Our results agree well with the theoretical and experimental results.

Effect of Hierarchical Architecture of Super-Hydrophobic Surface on the Condensed Drop's Final State

The interface free energy of a local condensate from the growth and combination of numerous initial condensation nuclei was calculated during its shape changes from an early flat shape to a Wenzel or Cassie state on the super-hydrophobic surface (SHS). The final state of the condensed drop was determined according to whether the interface free energy continuously decreased or it had a minimum value. Our calculations indicate that condensation drops on a surface only with micro roughness display Wenzel state because the interface free energy curve of a condensed drop first decreases and then increases, existing a minimum value corresponding to Wenzel drop. On a surface with appropriate hierarchical roughness, however, the interface energy curve of a condensed drop will constantly decline until it reaches the Cassie state. Therefore, a condensed drop on a hierarchical roughness surface can spontaneously reach the Cassie state. In addition, the states and apparent contact angles of condensed drops on a SHS with different structural parameters were calculated and compared with experimental observations. Results show that the calculated condensed drop states agree well with the experimental results. It can be concluded that micro and nano hierarchical roughness is the key structural factor responsible for sustaining condensed drops in the Cassie state on a SHS.

Number Fluctuations and Energy Dissipation in Sodium Spinor Condensates

We characterize fluctuations in atom number and spin populations in F=1 sodium spinor condensates. We find that the fluctuations enable a quantitative measure of energy dissipation in the condensate. The time evolution of the population fluctuations shows a maximum. We interpret this as evidence of a dissipation-driven separatrix crossing in phase space. For a given initial state, the critical time to the separatrix crossing is found to depend exponentially on the magnetic field and linearly on condensate density. This crossing is confirmed by tracking the energy of the spinor condensate as well as by Faraday rotation spectroscopy. We also introduce a phenomenological model that describes the observed dissipation with a single coefficient.

Diagnostics for the ground-state phase of a spin-2 Bose-Einstein condensate

We propose a method to determine the singlet-pair energy of a spin-2 Bose-Einstein condensate (BEC). By preparing the initial populations in the magnetic sublevels 0, 2, -2 with appropriate relative phases, we can obtain the coefficient of the spin singlet-pair term from the spin exchange dynamics. This method is suitable for hyperfine states with short lifetimes, since only the initial change in the population of each magnetic sublevel is needed. This method therefore enables the determination of the ground state phase of a spin-2 87Rb BEC at zero magnetic field, which is considered to lie in the immediate vicinity of the boundary between the antiferromagnetic and cyclic phases. We also show that the initial state in which relative phases are controlled can be prepared by Raman processes.