| 1. |
- Kavoulakis, Georgios, et al.
(författare)
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Superfluidity in a gas of strongly interacting bosons
- 2006
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Ingår i: Europhysics letters. - : Institute of Physics (IOP). - 0295-5075 .- 1286-4854. ; 76:2, s. 215-221
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Tidskriftsartikel (refereegranskat)abstract
- We consider small systems of bosonic atoms rotating in a toroidal trap. Using the method of exact numerical diagonalization of the many-body Hamiltonian, we examine the transition from the Bose-Einstein condensed state to the Tonks-Girardeau state. The system supports persistent currents in a wide range between the two limits, even in the absence of Bose-Einstein condensation.
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| 2. |
- Manninen, M., et al.
(författare)
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Vortex rings in two-dimensional harmonic traps
- 2006
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Ingår i: Physica Scripta. - 0031-8949. ; T125, s. 31-36
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Tidskriftsartikel (refereegranskat)abstract
- We use the configuration interaction technique to study vortex formation in rotating systems of interacting spinless fermions and bosons trapped in a two-dimensional harmonic potential. In the fermionic case, the vortices appear as holes in the Fermi sea and localize in rings. The yrast spectrum is dominated by rigid rotation of the vortex ring, showing periodic oscillations. The Bose system shows a similar yrast spectrum and vortex formation. This can be explained by a one-to-one correspondence of the fermion and boson many-particle configurations. A simple mean-field model can reproduce the oscillations in the yrast spectrum, but fails to explain the localization of vortices.
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| 3. |
- Reimann, Stephanie, et al.
(författare)
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Rotating quantum liquids crystallize
- 2006
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Small crystallites form when finite quantal systems are set highly rotating. This crystallization is independent of the statistics of the particles, and occurs for both trapped bosons and fermions. The spin degree of freedom does not change the tendency for localization. In a highly rotating state, the strongly correlated bosonic and fermionic systems approach to that of classical particles.
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| 4. |
- Reimann, Stephanie, et al.
(författare)
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Vortex localization in rotating clouds of bosons and fermions
- 2006
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Ingår i: Physical Review A. ; 74:4
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Tidskriftsartikel (refereegranskat)abstract
- Finite quantal systems at high angular momenta may exhibit vortex formation and localization. These phenomena occur independent of the statistics of the repulsively interacting particles, which may be of bosonic or fermionic nature. We analyze the relation between vortex localization and formation of stable Wigner molecules at high angular momenta in the view of particle-hole duality. Trial wave functions for the vortex states and the corresponding fermion-boson relations are discussed.
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| 5. |
- Räsänen, Esa, et al.
(författare)
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Giant vortices in rotating electron droplets
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. ; 73:23, s. 235324-235330
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Tidskriftsartikel (refereegranskat)abstract
- We predict the formation of giant vortices in quasi-two-dimensional quantum dots at high magnetic fields, i.e., in rapidly rotating electron droplets. Our numerical results for quantum dots confined by a flat, anharmonic potential show ground states where vortices are accumulated in the center of the dot, thereby leading to large cores in the electron and current densities. The phenomenon is analogous to what was recently found in rotating Bose-Einstein condensates. The giant-vortex states leave measurable signatures in the ground-state energetics. The conditions for the giant-vortex formation as well as the internal structure of the vortex cores are discussed.
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| 6. |
- Toreblad, Maria, et al.
(författare)
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Finite boson and fermion systems under extreme rotation: edge reconstruction and vortex formation
- 2006
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:12, s. 2721-2735
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Tidskriftsartikel (refereegranskat)abstract
- Vortices can form when finite quantal systems are set rotating. In the limit of small particle numbers, the vortex formation in a harmonically trapped fermion system, with repulsively interacting particles, shows similarities to the corresponding boson system, with vortices entering the rotating cloud for increasing rotation. For a larger number of fermions, N greater than or similar to 15, the fermion vortices compete and co-exist with (Chamon-Wen) edge-reconstructed ground states, forcing some ground states, as for example the central single vortex, into the spectrum of excited states. Experimentally, the fermion system could, for instance, be electrons in a semiconductor heterostructure, a quantum dot, and the corresponding boson system, a Bose-Einstein condensate in a magneto optical trap.
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| 7. |
- Ögren, Magnus, 1977-, et al.
(författare)
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Super-shell structure in harmonically trapped fermionic gases and its semi-classical interpretation
- 2006
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Ingår i: Physica Scripta. - : Royal Swedish Academy of Sciences. - 0031-8949 .- 1402-4896. ; :T125, s. 37-40
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Tidskriftsartikel (refereegranskat)abstract
- It was recently shown in self-consistent Hartree–Fock calculations that a harmonically trapped dilute gas of fermionic atoms with a repulsive two-body interaction exhibits 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 the beating mode depends on the strength of the interaction. We give a qualitative interpretation of the beat structure in terms of a semi-classical trace formula that uniformly describes the symmetry breaking U(3) → SO(3) in a three-dimensional harmonic oscillator potential perturbed by an anharmonic term ∝ r 4 with arbitrary strength. We show that at low Fermi energies (or particle numbers), the beating gross-shell structure of this system is dominated solely by the twofold degenerate circular and (diametrically) pendulating orbits.
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