| 1. |
- Karkkainen, K, et al.
(författare)
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Density-functional theory of multicomponent quantum dots
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:19
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Tidskriftsartikel (refereegranskat)abstract
- Quantum dots with conduction electrons or holes originating from several bands are considered. We assume the particles are confined in a harmonic potential and assume the electrons (or holes) belonging to different bands to be different types of fermions with isotropic effective masses. The density-functional method with the local density approximation is used. The increased number of internal (Kohn-Sham) states leads to a generalization of Hund's first rule at high densities. At low densitites the formation of Wigner molecules is favored by the increased internal freedom.
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| 2. |
- Karkkainen, K, et al.
(författare)
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Electron-hole bilayer quantum dots: phase diagram and exciton localization
- 2004
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Ingår i: Solid State Communications. - : Elsevier BV. - 1879-2766 .- 0038-1098. ; 130:3-4, s. 187-191
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Tidskriftsartikel (refereegranskat)abstract
- We studied a vertical 'quantum dot molecule', where one of the dots is occupied by electrons and the other by holes. We find that different phases occur in the ground state, depending on the carrier density and the interdot distance. When the system is dominated by shell structure, orbital degeneracies can be removed either by Hund's rule, or by Jahn-Teller deformation. Both mechanisms can lead to a maximum of the addition energy at mid-shell. At low densities and large interdot distances, bound electron-hole pairs are formed. (C) 2004 Elsevier Ltd. All rights reserved.
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| 3. |
- Karkkainen, K, et al.
(författare)
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Exchange-correlation energy of a multicomponent two-dimensional electron gas
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:20: 205322
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the exchange-correlation energy of a multicomponent (multivalley) two-dimensional (2D) electron gas and show that an extension of the recent parametrization [C. Attaccalite, S. Moroni, P. Gori-Giorgi, and G. B. Bachelet, Phys. Rev. Lett. 88, 256601 (2002)] of the exchange-correlation energy by Attaccalite describes well also the multicomponent system. We suggest a simple mass dependence of the correlation energy and apply it to study the phase diagram of the multicomponent 2D electron (or hole) gas. The results show that even a small mass difference of the components (e.g., heavy and light holes) decreases the concentration of the lighter components already at relatively high densities.
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| 4. |
- Koskinen, M, et al.
(författare)
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Spontaneous magnetism of quantum dot lattices
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 90:6: 066802
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Tidskriftsartikel (refereegranskat)abstract
- The magnetism of square lattices of quantum dots with up to 12 electrons per dot is studied using the spin-density functional formalism. At small values of the lattice constant, all lattices are nonmagnetic and gapless. When the lattice constant is increased, the shell structure of the single dots governs the magnetism of the lattice. At closed shells, the lattices are nonmagnetic and have a gap at the Fermi level. At the beginning and at the end of a shell, they become ferromagnetic and stay gapless up to large values of the lattice constant. Antiferromagnetism was observed only at midshell after a band gap was opened.
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| 5. |
- Toreblad, Maria, et al.
(författare)
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Universal vortex formation in rotating traps with bosons and fermions
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 93:9
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Tidskriftsartikel (refereegranskat)abstract
- We show that the rotation of trapped quantum mechanical particles with a repulsive interaction can lead to vortex formation, irrespective of whether the particles are bosons or (unpaired) fermions. The exact many-particle wave function constitutes similar structures in both cases, implying that this vortex formation is indeed universal.
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| 6. |
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| 7. |
- Reimann, Stephanie, et al.
(författare)
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Electronic structure of quantum dots
- 2002
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Ingår i: Reviews of Modern Physics. - 0034-6861. ; 74:4, s. 1283-1342
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Forskningsöversikt (refereegranskat)abstract
- The properties of quasi-two-dimensional semiconductor quantum dots are reviewed. Experimental techniques for measuring the electronic shell structure and the effect of magnetic fields are briefly described. The electronic structure is analyzed in terms of simple single-particle models, density-functional theory, and "exact" diagonalization methods. The spontaneous magnetization due to Hund's rule, spin-density wave states, and electron localization are addressed. As a function of the magnetic field, the electronic structure goes through several phases with qualitatively different properties. The formation of the so-called maximum-density droplet and its edge reconstruction is discussed, and the regime of strong magnetic fields in finite dot is examined. In addition, quasi-one-dimensional rings, deformed dots, and dot molecules are considered.
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| 8. |
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