| 1. |
- Brack, M., et al.
(författare)
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Uniform semiclassical trace formula for U(3) → SO(3) symmetry breaking
- 2005
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Ingår i: Journal of Physics A. - : Institute of Physics (IOP). - 0305-4470 .- 1361-6447. ; 38:46, s. 9941-9967
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Tidskriftsartikel (refereegranskat)abstract
- We develop a uniform semiclassical trace formula for the density of states of a three-dimensional isotropic harmonic oscillator (HO), perturbed by a term . This term breaks the U(3) symmetry of the HO, resulting in a spherical system with SO(3) symmetry. We first treat the anharmonic term for small ε in semiclassical perturbation theory by integration of the action of the perturbed periodic HO orbit families over the manifold which is covered by the parameters describing their four-fold degeneracy. Then, we obtain an analytical uniform trace formula for arbitrary ε which in the limit of strong perturbations (or high energy) asymptotically goes over into the correct trace formula of the full anharmonic system with SO(3) symmetry, and in the limit ε (or energy) →0 restores the HO trace formula with U(3) symmetry. We demonstrate that the gross-shell structure of this anharmonically perturbed system is dominated by the two-fold degenerate diameter and circular orbits, and not by the orbits with the largest classical degeneracy, which are the three-fold degenerate tori with rational ratios ωr:ωφ ≤ N:M of radial and angular frequencies. The same holds also for the limit of a purely quartic spherical potential V(r) ∝ r4.
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| 2. |
- Bulgac, A, et al.
(författare)
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Signatures of superfluidity in dilute fermi gases near a Feshbach resonance
- 2005
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Ingår i: Journal of Low Temperature Physics. - : Springer Science and Business Media LLC. - 0022-2291 .- 1573-7357. ; 138:3-4, s. 741-746
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Tidskriftsartikel (refereegranskat)abstract
- We present a brief account of the most salient properties of vortices in dilute atomic Fermi superfluids near a Feshbach resonance.
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| 3. |
- Cremon, Jonas, et al.
(författare)
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Rotational properties of a mixture of two Bose gases
- 2008
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- A rotating, two-component Bose-Einstein condensate is shown to exhibit vortices of multiple quantization, which are possible due to the interatomic interactions between the two species. Also, persistent currents are absent in this system. Finally, the order parameter has a very simple structure for a range of angular momenta.
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| 4. |
- 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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| 5. |
- Manninen, Matti, et al.
(författare)
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Electron-Hole Duality and Vortex Rings in Quantum Dots
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 94:10, s. 106405-106409
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Tidskriftsartikel (refereegranskat)abstract
- In a quantum-mechanical system, particle-hole duality implies that instead of studying particles, we can get equivalent information by studying the missing particles, the so-called holes. Using this duality picture for fermions in a rotating trap the vortices appear as holes in the Fermi sea. Here we predict that the formation of vortices in quantum dots at high magnetic fields causes oscillations in the energy spectrum which can be experimentally observed using accurate tunneling spectroscopy. We use the duality picture to show that these oscillations are caused by the localization of vortices in rings.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- Rontani, Massimo, et al.
(författare)
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Cold Fermionic Atoms in Two-Dimensional Traps: Pairing versus Hund's Rule
- 2009
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Ingår i: Physical Review Letters. - 1079-7114. ; 102:6, s. 1-060401
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Tidskriftsartikel (refereegranskat)abstract
- The microscopic properties of few interacting cold fermionic atoms confined in a two-dimensional (2D) harmonic trap are studied by numerical diagonalization. For repulsive interactions, a strong shell structure dominates, with Hund's rule acting at its extreme for the midshell configurations. In the attractive case, odd-even oscillations due to pairing occur simultaneously with deformations in the internal structure of the ground states, as seen from pair correlation functions.
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| 10. |
- 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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