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- Pinheiro, Fernanda, et al.
(author)
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Delocalization and superfluidity of ultracold bosonic atoms in a ring lattice
- 2013
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In: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:20, s. 205303-
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Journal article (peer-reviewed)abstract
- Properties of bosonic atoms in small systems with a periodic quasi-one-dimensional circular toroidal lattice potential subjected to rotation are examined by performing the exact diagonalization in a truncated many-body space. The expansion of the many-body Hamiltonian is considered in terms of the first-band Bloch functions, and no assumption regarding restriction to nearest neighbour hopping (tight-binding approximation) is involved. A finite size version of the zero temperature phase diagrams of Fisher et al (1989 Phys. Rev. B 40 546570) is obtained and the results, in remarkable quantitative correspondence with the results available for larger systems, discussed. Ground-state properties relating to superfluidity are examined in the context of two-fluid phenomenology. The basic tool, consisting of the intrinsic inertia associated with small rotation angular velocities in the lab frame, is used to obtain the ground state 'superfluid fractions' numerically. They are analytically associated with one-body, uniform solenoidal currents in the case of the adopted geometry. These currents are in general incoherent superpositions of contributions from each eigenstates of the associated reduced one-body densities, with the corresponding occupation numbers as weights. Full coherence occurs therefore only when only one eigenstate is occupied by all bosons. The obtained numerical values for the superfluid fractions remain small throughout the parameter region corresponding to the 'Mott insulator to superfluid' transition, and saturate at unity only as the lattice is completely smoothed out.
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| 2. |
- Pinheiro, Fernanda, et al.
(author)
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Quantum entanglement of bound particles under free center of mass dispersion
- 2012
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In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 85:6
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Journal article (peer-reviewed)abstract
- On the basis of the full analytical solution of the overall unitary dynamics, the time evolution of entanglement is studied in a simple bipartite model system evolving unitarily from a pure initial state. The system consists of two particles in one spatial dimension bound by harmonic forces and having its free center of mass initially localized in space in a minimum uncertainty wavepacket. The existence of such initial states in which the bound particles are not entangled is discussed. Galilean invariance of the system ensures that the dynamics of entanglement between the two particles is independent of the wavepacket mean momentum. In fact, as shown, it is driven by the dispersive center of mass free dynamics, and evolves in a time scale that depends on the interparticle interaction in an essential way.
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