| 1. |
- Bargi, Sara, et al.
(författare)
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Two-component Bose gases under rotation
- 2008
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Ingår i: Nuclei and Mesoscopic Physic. - : AIP. - 1551-7616 .- 0094-243X. ; 995, s. 25-33
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Konferensbidrag (refereegranskat)abstract
- We examine the formation of vortices in a one- and two-component gas of bosonic atoms in a harmonic trap that is set rotating. Both the mean-field Gross-Pitaevskii approach, and the numerical diagonalization method are employed. For a two-component Bose gas, we show that beside the well-known coreless vortices of single quantization, the interatomic interactions between the two species may lead to coreless vortices of multiple quantization. We furthermore comment on the geometries of the interlaced vortex patterns. In the limit of weak interactions, we finally demonstrate a number of exact results.
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| 2. |
- Capelle, Klaus, et al.
(författare)
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Energy gaps and interaction blockade in confined quantum systems
- 2007
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Ingår i: Physical Review Letters. - 1079-7114. ; 99:1, s. 010402-010406
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Tidskriftsartikel (refereegranskat)abstract
- We investigate universal properties of strongly confined particles that turn out to be dramatically different from what is observed for electrons in atoms and molecules. For a large class of harmonically confined systems, such as small quantum dots and optically trapped atoms, many-body particle addition and removal energies, and energy gaps, are accurately obtained from single-particle eigenvalues. Transport blockade phenomena are related to the derivative discontinuity of the exchange-correlation functional. This implies that they occur very generally, with Coulomb blockade being a particular realization of a more general phenomenon. In particular, we predict a van der Waals blockade in cold atom gases in traps.
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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. |
- Kärkkäinen, Kimmo, et al.
(författare)
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Bright solitary waves in a Bose-Einstein condensate and their interactions
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:3
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Tidskriftsartikel (refereegranskat)abstract
- We examine the dynamics of two bright solitary waves with a negative nonlinear term. The observed repulsion between two solitary waves-when these are in an antisymmetric combination-is attributed to conservation laws. Slight breaking of parity, in combination with weak relaxation of energy, leads the two solitary waves to merge. The effective repulsion between solitary waves requires certain nearly ideal conditions and is thus fragile.
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| 5. |
- Kärkkäinen, Kimmo, et al.
(författare)
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Magnetism and Hund's rule in an optical lattice with cold fermions
- 2007
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that a two-dimensional (2D) optical lattice loaded with repulsive, contact-interacting fermions shows a rich and systematic magnetic phase diagram. Trapping a few (N <= 12) fermions in each of the single-site minima of the optical lattice, we find that the shell structure in these quantum wells determines the magnetism. In a shallow lattice, the tunnelling between the single wells is strong, and the lattice is non-magnetic (NM). For deeper lattices, however, the shell filling of the single wells with fermionic atoms determines the magnetism. As a consequence of Hund's first rule, the interaction energy is lowered by maximizing the number of atoms of the same species. This leads to a systematic sequence of NM, ferromagnetic (F) and antiferromagnetic (AF) phases.
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| 6. |
- Kärkkäinen, Kimmo, et al.
(författare)
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Magnetism in artificial lattices
- 2007
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 43:1-3, s. 225-228
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Tidskriftsartikel (refereegranskat)abstract
- We compare magnetism in two artificial lattice structures, a quantum dot array formed in a two-dimensional electron gas and an optical lattice loaded with repulsive, contact-interacting fermionic atoms. When the tunneling between the lattice sites is strong, both lattices are non-magnetic. With reduced tunneling in the tight-binding limit, the shell-filling of the single-site quantum wells combined with Hund's rule determines the magnetism. This leads to a systematic magnetic phase diagram with non-magnetic, ferromagnetic and antiferromagnetic phases.
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| 7. |
- Kärkkäinen, Kimmo, et al.
(författare)
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Magnetism in one-dimensional quantum dot arrays
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 72:16, s. 165324-165330
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Tidskriftsartikel (refereegranskat)abstract
- We employ the density functional Kohn-Sham method in the local spin-density approximation to study the electronic structure and magnetism of quasi-one-dimensional periodic arrays of few-electron quantum dots. At small values of the lattice constant, the single dots overlap, forming a nonmagnetic quantum wire with nearly homogenous density. As the confinement perpendicular to the wire is increased, i.e., as the wire is squeezed to become more one dimensional, it undergoes a spin-Peierls transition. Magnetism sets in as the quantum dots are placed farther apart. It is determined by the electronic shell filling of the individual quantum dots. At larger values of the lattice constant, the band structure for odd numbers of electrons per dot indicates that the array could support spin-polarized transport and therefore act as a spin filter.
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| 8. |
- Kärkkäinen, Kimmo, et al.
(författare)
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Metastability of persistent currents in trapped gases of atoms
- 2007
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Ingår i: Physical Review A. ; 76, s. 043627-043633
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Tidskriftsartikel (refereegranskat)abstract
- We examine the conditions that give rise to metastable, persistent currents in a trapped Bose-Einstein condensate. A necessary condition for the stability of persistent currents is that the trapping potential is not a monotonically increasing function of the distance from the trap center. Persistent currents also require that the interatomic interactions are sufficiently strong and repulsive. Finally, any off-center vortex state is shown to be unstable, while a driven gas shows hysteresis.
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| 9. |
- Maron, Eduard, et al.
(författare)
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Manifesto for an international digital mental health network
- 2019
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Ingår i: Digital Psychiatry. - 2575-517X. ; :1
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Tidskriftsartikel (refereegranskat)abstract
- Current mental health services across the world remain expert-centric and are based on traditional workflows, mostly using impractical and ineffective electronic record systems or even paper-based documentation. The international network for digital mental health (IDMHN) is comprised of top-level clinicians, regulatory and ICT experts, genetic scientists, and support organizations. The IDMHN has been formed to enable the implementation of digital innovations in clinical practice, hereby facilitating the transformation of current mental health services to be more personalized and more responsive to patients and healthcare needs. This consensus statement summarizes the consortium’s vision and strategy for further development of digital mental Health.
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| 10. |
- Smyrnakis, J., et al.
(författare)
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Mixtures of Bose Gases Confined in a Ring Potential
- 2009
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Ingår i: Physical Review Letters. - 1079-7114. ; 103:10
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Tidskriftsartikel (refereegranskat)abstract
- The rotational properties of a mixture of two distinguishable Bose gases that are confined in a ring potential provide novel physical effects that we demonstrate in this study. Persistent currents are shown to be stable for a range of the population imbalance between the two components at low angular momentum. At higher values of the angular momentum, even small admixtures of a second species of atoms make the persistent currents highly fragile.
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