| 1. |
- Fransson, Jonas, et al.
(författare)
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A perfect spin-filter quantum dot system
- 2004
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Ingår i: Journal of Physics. - 0953-8984 .- 1361-648X. ; 16:16, s. L249-L254
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of a novel effect in the transport through a QD spin-dependently coupled to magnetic contacts is reported. For a finite range of source-drain voltages the spin projections of the current cancel exactly, resulting in a completely suppressed output current. The spin down current behaves as one normally expects whereas the spin up current becomes negative. As the source-drain voltage is increased the spin up current eventually becomes positive. Thus, tuning the source-drain voltage such that the spin up current vanishes will result in a perfect spin filter.
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| 2. |
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| 3. |
- Fransson, Jonas, et al.
(författare)
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Effects of nonorthogonality in the time-dependent current through tunnel junctions
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 64:15, s. 153403-
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical technique which allows one to include contributions from nonorthogonality of the electron states in the leads connected to a tunneling junction is derived. The theory is applied to a single-barrier, tunneling structure and a simple expression for the time-dependent tunneling current is derived showing explicit dependence of the overlap. The overlap proves to be necessary for a better quantitative description of the tunneling current, and our theory reproduces experimental results substantially better compared to standard approaches.
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| 4. |
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| 5. |
- Fransson, Jonas, et al.
(författare)
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Transport through quasi-degenerate states in coupled quantum dots
- 2004
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Ingår i: Photonics and Nanostructures - Fundamentals and Applications. - : Elsevier BV. - 1569-4410. ; 2:1, s. 11-21
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Tidskriftsartikel (refereegranskat)abstract
- By means of a general method for treating mesoscopic systems with strong internal correlations, transport properties through a set of quasi-degenerate transitions in the interacting region, or active element (AE), are considered. It is shown that the behaviour of the AE drastically changes as the couplings to the contacts are varied from the strong to the weak coupling limit. These changes strongly influence the transport properties of the system, from a single increase of the current to a staircase form with unequally large steps. In the present study, kinematic interactions, non-equilibrium populations numbers and dependence on the bias voltage has been included in the treatment of the local properties of the AE. Analytical results for the equilibrium situation are presented as well as a derivation of the corresponding non-equilibrium quantities. Results from self-consistent numerical calculations of the considered case are presented.
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| 6. |
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| 7. |
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| 8. |
- Lundin, U, et al.
(författare)
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Are there two types of f-electrons in Pr-metal?
- 1999
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Ingår i: PHYSICA B. - : ELSEVIER SCIENCE BV. - 0921-4526. ; 261, s. 231-232
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We show that in order to properly describe the bonding properties of strongly correlated systems, here demonstrated for praseodymium metal, it is necessary to split the f-electron system into two parts. Using perturbation theory from the atomic limit we s
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| 9. |
- Lundin, U, et al.
(författare)
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Correlation mechanism of f-electron delocalization
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:24, s. 16370-16377
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism off-electron delocalization is investigated within the multiorbital Anderson lattice model by means of diagrammatic perturbation theory from the atomic limit. The derived equations couple the intraatomic transition energies, their spectral weights, and the population numbers of the many-electron states. A self-consistent solution for praseodymium metal shows that the delocalization can be caused by external pressure via a resonant mixing off and conduction electrons in the vicinity of the the Fermi surface. We also find the following. (1) An increase of mixing leads to a decrease of the physical values of the Hubbard interactions U*, the reduction, however, is small. (2) The initial Hubbard U is split by renormalization into a set of different physical values of U*(i,j). (3) The gain in cohesive energy together with the f-sum rule cause a transfer of spectral weight, which is decisive for the delocalization off electrons. (4) The correlated fermionic quasiparticles have their bandwidth slightly reduced compared to those obtained using the Kohn-Sham equation.
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| 10. |
- Lundin, U, et al.
(författare)
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Correlation mechanism of f-electron delocalization
- 2000
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Ingår i: PHYSICAL REVIEW B. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 62:24, s. 16370-16377 Language: English
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism off-electron delocalization is investigated within the multiorbital Anderson lattice model by means of diagrammatic perturbation theory from the atomic limit. The derived equations couple the intraatomic transition energies, their spectral w
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