10 research outputs found
Pauli crystals -- interplay of symmetries
Recently observed Pauli crystals are structures formed by trapped ultracold
atoms with the Fermi statistics. Interactions between these atoms are switched
off, so their relative positions are determined by joined action of the
trapping potential and the Pauli exclusion principle. Numericalmodeling is used
in this paper to find the Pauli crystals in a two-dimensional isotropic
harmonic trap, three-dimensional harmonic trap, and a two-dimensional square
well trap. The Pauli crystals do not have the symmetry of the trap -- the
symmetry is broken by the measurement of positions and, in many cases, by the
quantum state of atoms in the trap. Furthermore, the Pauli crystals are
compared with the Coulomb crystals formed by electrically charged trapped
particles. The~structure of the Pauli crystals differs from that of the Coulomb
crystals, this provides evidence that the exclusion principle cannot be
replaced by a two-body repulsive interaction but rather has to be considered to
be a specifically quantum mechanism leading to many-particle correlations.Comment: This article belongs to the Special Issue "Symmetries and the Pauli
Exclusion Principle
Manifestation of relative phase in dynamics of two interacting Bose-Bose droplets
We study coherent dynamics of two interacting Bose-Bose droplets by means of the extended Gross-Pitaevskii equation. The relative motion of the droplets couples to the phases of their components. The dynamics can be understood in terms of the evolution of zero-energy modes recovering symmetries spontaneously broken by the mean-field solution. These are translational symmetry and two U(1) symmetries, associated with the phases of the droplets' two components. A phase-dependent interaction potential and double Josephson-junction equations are introduced to explain the observed variety of different scenarios of collision. We show that the evolution of the droplets is a macroscopic manifestation of the hidden dynamics of their phases. The occurrence of nondissipative drag between the two supercurrents (Andreev-Bashkin effect) is mentioned
Quantum droplets in a dipolar Bose gas at a dimensional crossover
We study the beyond-mean-field corrections to the energy of a dipolar Bose gas confined to two dimensions by a box potential with dipoles oriented in plane such that their interaction is anisotropic in the two unconfined dimensions. At a critical strength of the dipolar interaction the system becomes unstable on the mean field level. We find that the ground state of the gas is strongly influenced by the corrections, leading to formation of a self-bound droplet, in analogy to the free space case. Properties of the droplet state can be found by minimizing the extended Gross-Pitaevskii energy functional. In the limit of strong confinement we show analytically that the correction can be interpreted as an effective three-body repulsion which stabilizes the gas at finite density