| 1. |
- Berggren, Karl-Fredrik, et al.
(författare)
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Effects of exchange and electron correlation on conductance and nanomagnetism in ballistic semiconductor quantum point contacts
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:8
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Tidskriftsartikel (refereegranskat)abstract
- The spontaneous magnetization of a quantum point contact (QPC) formed between two large quantum dots by a lateral confinement of a high-mobility two-dimensional electron gas is studied for a realistic GaAs/AlxGa1-xAs heterostructure. The model of the device incorporates the contributions from a patterned gate, doping, surface states, and mirror charges. To explore the magnetic properties, the Kohn-Sham local spin-density formalism is used with exchange and correlation potentials that allows for local spin polarization. Exchange is the dominant mechanism behind local magnetization within the QPC, while the correlation part is less prominent. However, the correlation potential gives rise to an important correction in the QPC potential. Below the first conduction plateau we thus find a magnetized regime corresponding approximately to a single electron spin. Using an approximate separable saddle potential we compute the conductance and recover the so-called similar to0.7 (2e(2)/h) conduction anomaly plus an additional anomaly at similar to0.4 (2e(2)/h) below which the magnetization collapses.
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| 2. |
- Starikov, Anton, et al.
(författare)
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Scenario for the 0.7-conductance anomaly in quantum point contacts
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:23
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Tidskriftsartikel (refereegranskat)abstract
- Effects of spontaneous spin polarization in quantum point contacts (QPC's) are investigated for a realistic semiconductor device structure using the Kohn-Sham local spin-density formalism. At maximal polarization in the contact area, there is a bifurcation into ground-state and metastable solutions. The conduction associated with the metastability is lower than for the normal state. With increasing temperature, the conductance should therefore show an anomalous behavior as observed. For the present device we do not recover resonance or quasibound states.
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| 3. |
- Yakimenko, II, et al.
(författare)
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Symmetry and spin polarization in single and coupled quantum dots
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 63:16, s. art. no.-165309
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Tidskriftsartikel (refereegranskat)abstract
- We conducted theoretical investigation into the effect of spontaneous electron spin polarization in single and coupled quantum dots formed by lateral confinement of a high-mobility two-dimensional electron gas in a semiconductor heterostructure. The equilibrium properties of realistic many-electron quantum-dot devices are first studied within the two-dimensional Thomas-Fermi approximation taking into account contributions from the patterned gate, doping, surface states, and mirror charges. In order to explore spin-dependent phenomena, a self-consistent model has been developed using the Kohn-Sham local spin-density formalism. We have tested the contribution of electron correlation in the systems considered and found that it plays a minor role, hence only exchange interactions are included in the model. We investigate the possibilities of manipulating the magnetization (spin polarization) of single and double quantum dots by means of their mutual coupling and symmetry breaking caused by variations in the geometry of the gate.
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