| 1. |
- Berggren, Karl-Fredrik, et al.
(författare)
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On the role of electron exchange and correlation in semiconductor quantum dots
- 2001
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 12:4, s. 529-532
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Spontaneous magnetization of single and coupled quantum dots formed by lateral confinement of a high-mobility two-dimensional electron gas is studied for a realistic GaAs/AlGaAs heterostructure. The modelling of the device takes into account contributions from a patterned gate, doping, surface states, and mirror charges. To explore the magnetic properties we use the Kohn-Sham local spin-density formalism including the contributions from electron correlation and exchange. We show by explicit calculations that the exchange is the dominant mechanism driving a spontaneous magnetization of a dot. The correlation potential reduces the amount of level splitting and usually affects the electron content in the dot at a given gate voltage. These effects are, however, small and may be neglected under present circumstances. Single dots with up to 50 electrons have been studied.
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| 2. |
- Berggren, Karl-Fredrik, et al.
(författare)
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Quantum chaos among nodal points and streamlines at ballistic electron transport through open quantum dots
- 2001
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 12:4, s. 562-565
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We trace signatures of quantum chaos in the distribution of nodal points and streamlines for coherent electron transport through different types of quantum dots (chaotic and regular). We have calculated normalized distribution functions for the nearest distances between nodal points and found that this distribution may be used as a signature of quantum chaos for electron transport in open systems. Different chaotic billiards show the same characteristic distribution function for nodal points. This signature of quantum chaos is well reproduced using well known approaches for chaotic wavefunctions. We have also investigated the quantum flows which display some remarkable features.
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| 3. |
- Bychkov, A.M., et al.
(författare)
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Spin-dependent electron behaviour in quantum point contacts
- 2000
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 11:4, s. 318-322
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Tidskriftsartikel (refereegranskat)abstract
- The effect of spontaneous spin polarization in quantum point contacts (QPCs) is investigated by self-consistent modelling within the Kohn-Sham local spin-density formalism. The existence of the spin-polarized state of the QPC channel in the low-density regime is shown to change the value and the shape of the effective potential barrier for up- and down-spin electrons. We suggest that this effect can be relevant to the explanation of the anomalous 0.7-structure in the QPC conductance and may assist spin injection in potential spintronic devices.
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| 4. |
- Heyman, A., et al.
(författare)
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Band structure and spin polarization for a one-dimensional array of quantum point contacts
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 15:1, s. 143-148
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Tidskriftsartikel (refereegranskat)abstract
- We have numerically studied the band structure and the spin polarization effect in a periodic one-dimensional array of quantum point contacts (QPCs) formed in a two-dimensional electron gas in a plane-layered semiconductor system. In this study we used a self-consistent model developed within the framework of the Kohn-Sham local spin-density formalism. We have found that the band structure contains a mixture of flat and dispersed bands, and the role of transverse modes in the formation of such a band structure has been clearly demonstrated. We have also shown that spin polarization occurs mainly in the regions occupied by the QPCs and that it is qualitatively similar to the spin polarization in a single QPC.
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| 5. |
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| 6. |
- Macucci, M., et al.
(författare)
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Status and perspectives of nanoscale device modelling
- 2001
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 12:2, s. 136-142
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During the meetings of the theory and modelling working group, within the MEL-ARI (Microelectronics Advanced Research Initiative) and NID-FET (Nanotechnology Information Devices-Future and Emerging Technologies) initiatives of the European Commission, we have been discussing the current status and the future perspectives of nanoscale device modelling. The outcome of such a discussion is summarized in the present paper, outlining the major challenges for the future, such as the integration of nonequilibrium phenomena and of molecular-scale properties. We believe that modelling has a growing importance in the development of nanoelectronic devices and must therefore make a move from physics to engineering, providing valid design tools, with quantitative predictive capabilities.
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