Phonon-Josephson resonances in atomtronic circuits

We study the resonant excitation of sound modes from Josephson oscillations in Bose-Einstein condensates. From the simulations for various setups using the Gross-Pitaevskii mean-field equations and Josephson equations we observe additional tunneling currents induced by resonant phonons. The proposed experiment may be used for spectroscopy of phonons as well as other low-energy collective excitations in Bose-Einstein condensates. We also argue that the observed effect may mask the observation of Shapiro resonances if not carefully controlled.Comment: 8 pages, 11 figures. Updated to match the published versio

JM-ECS: A hybrid method combining the JJ-matrix and ECS methods for scattering calculations

The paper proposes a hybrid method for calculating scattering processes that combines the $J$-matrix method with exterior complex scaling as an absorbing boundary condition. It represents the wave function as a finite sum of oscillator eigenstates in the inner region and on grid in the outer region. The method is validated for one and two dimensional model partial wave equation equations. Finally, the method calculates nuclear $p$-shell scattering

Can tetraneutron exist from theoretical point of view?

A theoretical possibility is shown for the bound state of a tetraneutron to exist in the case of the proposed neutron-neutron potentials in the singlet state with two attractive wells separated by a repulsive barrier. The anomalous behaviours are revealed for the calculated size, density distribution, and pair correlation functions of a hypothetical tetraneutron.Comment: 8 pages including 3 figure

Finite-temperature dynamics of a bosonic Josephson junction

In the framework of the stochastic projected Gross-Pitaevskii equation we investigate finite-temperature dynamics of a bosonic Josephson junction (BJJ) formed by a Bose-Einstein condensate of atoms in a two-well trapping potential. We extract the characteristic properties of the BJJ from the stationary finite-temperature solutions and compare the dynamics of the system with the resistively shunted Josephson model. Analyzing the decay dynamics of the relative population imbalance we estimate the effective normal conductance of the junction induced by thermal atoms. The calculated normal conductance at various temperatures is then compared with predictions of the noise-less model and the model of ballistic transport of thermal atoms.Comment: This is the version of the article before peer review or editing, as submitted by authors to Journal of Physics B: Atomic, Molecular and Optical Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6455/aae02

Energy Thresholds of Stability of Three-Particle Systems

We have studied the general properties of the energy thresholds of stability for a three-particle system with short-range interaction. A wide region of the interaction constants and various ratios of the masses of particles are considered. The specific effects characteristic of the near-threshold stationary energy levels of three particles are revealed. The asymptotic estimates are obtained for the thresholds at some limiting cases, and the high-precision variational calculations of the thresholds for various values of the interaction constants and the masses of particles are carried out.Comment: 27 pages, 6 PostScript figures, RevTeX

Projected Gross-Pitaevskii equation for ring-shaped Bose-Einstein condensates

We propose an alternative implementation of the Projected Gross-Pitaevskki equation adapted for numerical modeling of the atomic Bose-Einstein condensate trapped in a toroidally-shaped potential. We present an accurate and efficient scheme to evaluate the required matrix elements and calculate time evolution of the matter wave field. We analyze the stability and accuracy of the developed method for equilibrium and nonequilibrium solutions in a ring-shaped trap with additional barrier potential corresponding to recent experimental realizations

Symmetry breaking and phase transitions in Bose-Einstein condensates with spin-orbital-angular-momentum coupling

Theoretical study is presented for a spinor Bose-Einstein condensate, whose two components are coupled by copropagating Raman beams with different orbital angular momenta. The investigation is focused on the behavior of the ground state of this condensate, depending on the atom-light coupling strength. By analyzing the ground state, we have identified a number of quantum phases, which reflect the symmetries of the effective Hamiltonian and are characterized by the specific structure of the wave function. In addition to the well-known stripe, polarized and zero-momentum phases, our results show that the system can support phases, whose wave function contains a complex vortex molecule. Such molecule plays an important role in the continuous phase transitions of the system. The predicted behavior of vortex-molecule phases can be examined in cold-atom experiments using currently existing techniques

Stable Hopf solitons in rotating Bose-Einstein condensates

We reveal that Hopf solitons can be stabilized in rotating atomic Bose-Einstein condensate. The Hopfion is a matter-wave vortex complex which carries two independent winding numbers. Such a topological solitonic structure results from a superfluid flow of atoms simultaneously quantized in poloidal and toroidal directions. In the framework of a dissipative mean-field model we observe different unstable evolution scenarios of the Hopfions. We demonstrate energetic and dynamical stability of the Hopf solitons under experimentally feasible conditions.Comment: 5 pages, 10 figure

Collective excitations and tunneling dynamics in long bosonic Josephson junctions

We investigate the low-energy dynamics of two coupled anisotropic Bose-Einstein condensates forming a long Josephson junction. The theoretical study is performed in the framework of the two-dimensional Gross-Pitaevskii equation and the Bogoliubov-de Gennes formalism. We analyze the excitation spectrum of the coupled Bose condensates and show how low-energy excitations of the condensates lead to multiple-frequency oscillations of the atomic populations in the two wells. This analysis generalizes the standard bosnic Josephson euqation approach. We also develop a one-dimensional hydrodynamic model of the coupled condensates, that is capable to reproduce the excitation spectrum and population dynamics of the system

Dispersion relations and self-localization of quasiparticles in coupled elongated Bose-Einstein condensates

We present a detailed study of the spectrum and dispersion of Bogoliubov quasiparticles in two coupled elongated Bose-Einstein condensates. We develop an analytically solvable model that approximates two infinite homogeneous condensates and compare its predictions to a numerical simulation of a realistic trapped system. While the comparisons show a reasonable agreement between the two models, they also manifest the existence of several anomalous Bogoliubov modes in the spectrum. These modes show degeneracy in both energy and momentum together with self-localization in the coordinate space