| 1. |
- Deuretzbacher, F., et al.
(författare)
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Self-bound many-body states of quasi-one-dimensional dipolar Fermi gases : Exploiting Bose-Fermi mappings for generalized contact interactions
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 88:3, s. 033611-
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Tidskriftsartikel (refereegranskat)abstract
- Using a combination of results from exact mappings and from mean-field theory we explore the phase diagram of quasi-one-dimensional systems of identical fermions with attractive dipolar interactions. We demonstrate that at low density these systems provide a realization of a single-component one-dimensional Fermi gas with a generalized contact interaction. Using an exact duality between one-dimensional Fermi and Bose gases, we show that when the dipole moment is strong enough, bound many-body states exist, and we calculate the critical coupling strength for the emergence of these states. At higher densities, the Hartree-Fock approximation is accurate, and by combining the two approaches we determine the structure of the phase diagram. The many-body bound states should be accessible in future experiments with ultracold polar molecules.
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| 2. |
- Yu, Yongle, et al.
(författare)
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Supershell structure in trapped dilute Fermi gases
- 2005
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 72:5
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Tidskriftsartikel (refereegranskat)abstract
- We show that a dilute harmonically trapped two-component gas of fermionic atoms with a weak repulsive interaction has a pronounced super-shell structure: The shell fillings due to the spherical harmonic trapping potential are modulated by a beat mode. This changes the "magic numbers" occurring between the beat nodes by half a period. The length and amplitude of this beating mode depend on the strength of the interaction. We give a simple interpretation of the beat structure in terms of a semiclassical trace formula for the symmetry breaking U(3)→SO(3).
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| 3. |
- Bargi, Sara, et al.
(författare)
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Persistent currents in Bose gases confined in annular traps
- 2010
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 82:4
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Tidskriftsartikel (refereegranskat)abstract
- We examine the problem of stability of persistent currents in a mixture of two Bose gases trapped in an annular potential. We evaluate the critical coupling for metastability in the transition from quasi-one- to two-dimensional motion. We also evaluate the critical coupling for metastability in a mixture of two species as a function of the population imbalance. The stability of the currents is shown to be sensitive to the deviation from one-dimensional motion.
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| 4. |
- Bargi, Sara, et al.
(författare)
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Rotating Bose-Einstein condensates confined in an anharmonic potential
- 2006
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 73:3: 033613
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Tidskriftsartikel (refereegranskat)abstract
- We consider bosonic atoms that rotate in an anharmonic trapping potential. Using numerical diagonalization of the Hamiltonian, we get evidence for various phases of the gas for different values of the coupling between the atoms and of the rotational frequency of the trap. These include vortex excitation of single and multiple quantization, the phase of center-of-mass excitation, and the unstable phase.
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| 5. |
- Borgh, Magnus, et al.
(författare)
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Universality of many-body states in rotating Bose and Fermi systems
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 77:3
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Tidskriftsartikel (refereegranskat)abstract
- We propose a universal transformation from a many-boson state to a corresponding many-fermion state in the lowest-Landau-level approximation of rotating many-body systems, inspired by the Laughlin wave function and by the Jain composite-fermion construction. We employ the exact-diagonalization technique for finding the many-body states. The overlap between the transformed boson ground state and the true fermion ground state is calculated in order to measure the quality of the transformation. For very small and high angular momenta, the overlap is typically above 90%. For intermediate angular momenta, mixing between states complicates the picture and leads to small ground-state overlaps at some angular momenta.
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| 6. |
- Christensson, J, et al.
(författare)
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Effective-interaction approach to the many-boson problem
- 2009
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934 .- 1050-2947. ; 79:1, s. 012707-
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Tidskriftsartikel (refereegranskat)abstract
- We show that the convergence behavior of the many-body numerical diagonalization scheme for strongly interacting bosons in a trap can be significantly improved by the Lee-Suzuki method adapted from nuclear physics: One can construct an effective interaction that acts in a space much smaller than the original Hilbert space. In particular for short-ranged forces and strong correlations, the method offers a good estimate of the energy and the excitation spectrum, at a computational cost several orders of magnitude smaller than that required by the standard method.
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| 7. |
- Cremon, Jonas, et al.
(författare)
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Rotating Bose-Einstein condensates: Closing the gap between exact and mean-field solutions
- 2015
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 91:3
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Tidskriftsartikel (refereegranskat)abstract
- When a Bose-Einstein-condensed cloud of atoms is given some angular momentum, it forms vortices arranged in structures with a discrete rotational symmetry. For these vortex states, the Hilbert space of the exact solution separates into a "primary" space related to the mean-field Gross-Pitaevskii solution and a "complementary" space including the corrections beyond mean field. Considering a weakly interacting Bose-Einstein condensate of harmonically trapped atoms, we demonstrate how this separation can be used to close the conceptual gap between exact solutions for systems with only a few atoms and the thermodynamic limit for which the mean field is the correct leading-order approximation. Although we illustrate this approach for the case of weak interactions, it is expected to be more generally valid.
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| 8. |
- Cremon, Jonas, et al.
(författare)
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Vortices in Bose-Einstein condensates: Finite-size effects and the thermodynamic limit
- 2013
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 87:5
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Tidskriftsartikel (refereegranskat)abstract
- For a weakly interacting Bose gas rotating in a harmonic trap we relate the yrast states of small systems (that can be treated exactly) to the thermodynamic limit (derived within the mean-field approximation). For a few dozens of atoms, the yrast line shows distinct quasiperiodic oscillations with increasing angular momentum that originate from the internal structure of the exact many-body states. These finite-size effects disappear in the thermodynamic limit, where the Gross-Pitaevskii approximation provides the exact energy to leading order in the number of particles N. However, the exact yrast states reveal significant structure not captured by the mean-field approximation: Even in the limit of large N, the corresponding mean-field solution accounts for only a fraction of the total weight of the exact quantum state.
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| 9. |
- Deuretzbacher, F., et al.
(författare)
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Ground-state properties of few dipolar bosons in a quasi-one-dimensional harmonic trap
- 2010
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 81:6
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Tidskriftsartikel (refereegranskat)abstract
- We study the ground state of few bosons with repulsive dipole-dipole interaction in a quasi-one-dimensional harmonic trap by means of the exact diagonalization method. Up to three interaction regimes are found, depending on the strength of the dipolar interaction and the ratio of transverse to axial oscillator lengths: a regime where the dipolar Bose gas resembles a system of weakly delta-interacting bosons, a second regime where the bosons are fermionized, and a third regime where the bosons form a Wigner crystal. In the first two regimes, the dipole-dipole potential can be replaced by a delta potential. In the crystalline state, the overlap between the localized wave packets is strongly reduced and all the properties of the boson system equal those of its fermionic counterpart. The transition from the Tonks-Girardeau gas to the solidlike state is accompanied by a rapid increase of the interaction energy and a considerable change of the momentum distribution, which we trace back to the different short-range correlations in the two interaction regimes.
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| 10. |
- Deuretzbacher, F., et al.
(författare)
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Quantum magnetism without lattices in strongly interacting one-dimensional spinor gases
- 2014
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 90:1
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Tidskriftsartikel (refereegranskat)abstract
- We show that strongly interacting multicomponent gases in one dimension realize an effective spin chain, offering an alternative simple scenario for the study of one-dimensional (1D) quantum magnetism in cold gases in the absence of an optical lattice. The spin-chain model allows for an intuitive understanding of recent experiments and for a simple calculation of relevant observables. We analyze the adiabatic preparation of antiferromagnetic and ferromagnetic ground states, and show that many-body spin states may be efficiently probed in tunneling experiments. The spin-chain model is valid for more than two components, opening the possibility of realizing SU(N) quantum magnetism in strongly interacting 1D alkaline-earth-metal or ytterbium Fermi gases.
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