| 1. |
- Ekenberg, Ulf, et al.
(författare)
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Analysis of electric-field-induced spin splitting in wide modulation-doped quantum wells
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:20, s. 205317-
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the proper inclusion of electric-field-induced spin splittings in the framework of the envelope function approximation. We argue that the Rashba effect should be included in the form of a macroscopic potential as diagonal terms in a multiband approach rather than the commonly used Rashba term dependent on k and electric field. It is pointed out that the expectation value of the electric field in a subband is sometimes not unique because the expectation values can even have opposite signs for the spin-split subband components. Symmetric quantum wells with Dresselhaus terms and the influence of the interfaces on the spin splitting are also discussed. We apply a well established multiband approach to wide modulation-doped InGaSb quantum wells with strong built-in electric fields in the interface regions. We demonstrate an efficient mechanism for switching on and off the Rashba splitting with an electric field being an order of magnitude smaller than the local built-in field that determines the Rashba splitting. The implications of our findings for spintronic devices, in particular the Datta-Das spin transistor and proposed modifications of it, are discussed.
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| 2. |
- Gvozdic, D. M., et al.
(författare)
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Comparison of performance of n- and p-type spin transistors with conventional transistors
- 2005
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Ingår i: Journal of Superconductivity. - : Springer Science and Business Media LLC. - 0896-1107 .- 1572-9605. ; 18:3, s. 349-356
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Tidskriftsartikel (refereegranskat)abstract
- A spintronic device that has stimulated much research interest is the Datta-Das spin transistor. The mechanism behind it called the Rashba effect is that an applied voltage gives rise to a spin splitting. We propose ways to optimize this effect. The relevant spin splitting in k-space is predicted to increase with electric field at a rate that is more than two orders of magnitude larger for holes than for electrons. Furthermore, the almost negligible lattice-mismatch between GaAs and AlGaAs can be used to further enhance the advantage of hole-based spin transistors. Compared to present transistors we conclude that electron-based spin transistors will have problems to become competitive but hole-based ones are much more promising.
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| 3. |
- Gvozdic, D. M., et al.
(författare)
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Efficient switching of Rashba spin splitting in wide modulation-doped quantum wells
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:5
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Tidskriftsartikel (refereegranskat)abstract
- The authors demonstrate that the size of the electric-field-induced Rashba spin splitting in an 80 nm wide modulation-doped InGaSb quantum well can depend strongly on the spatial variation of the electric field. In a slightly asymmetric quantum well it can be an order of magnitude stronger than for the average uniform electric field. For even smaller asymmetry spin subbands can have wave functions and/or expectation values of the spin direction that are completely changed as the in-plane wave vector varies. The Dresselhaus effect [Phys. Rev. 100, 580 (1955)] can give an anticrossing at which the spin rapidly flips.
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| 4. |
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| 5. |
- Gvozdić, D. M., et al.
(författare)
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Novel mechanism for rapid spin flip with increasing in-plane wave vector in slightly asymmetric modulation-doped quantum wells
- 2008
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Ingår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY. - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- We calculate the electric-field-induced spin splittings in wide slightly asymmetric modulation-doped quantum wells. When spin subbands are anticrossing we demonstrate twostep spin flips as the in-plane wave vector along the [11] direction is increased by 0.002 nm-1. At the beginning of this interval the y-component flips, at the end the x-component. Simultaneously the energy separation stays roughly constant below 1-eV and the wave functions are interchanged. A bias change of about 1 meV is sufficient to move the Fermi level from below to above the anticrossing region.
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| 6. |
- Gvozdic, D. M., et al.
(författare)
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Strong dependence of spin direction and wave function localization on In-plane wave vector in wide modulation-doped quantum wells
- 2007
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 61:1, s. 273-277
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Tidskriftsartikel (refereegranskat)abstract
- An important mechanism in spintronics is spin-splitting induced by structure and/or bulk inversion asymmetry. These effects are frequently assumed to depend on two parameters usually denoted by α and β respectively, and α is assumed to be proportional to some average electric field. We here demonstrate that the spatial dependence of the electric field gives very important effects absent in simpler models. These effects are particularly clear in wide modulation-doped quantum wells where there are two weakly interacting electron gases in the interface regions. Using an 8 × 8 k . p matrix approach we obtain anticrossings between interacting subbands at which the spin direction and/or wave function localization are found to be strong functions of the in-plane wave vector.
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| 7. |
- Gvozdic, D. M., et al.
(författare)
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Superefficient electric-field-induced spin-orbit splitting in strained p-type quantum wells
- 2006
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 73:6, s. 927-933
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Tidskriftsartikel (refereegranskat)abstract
- We investigate theoretically the efficiency of the Rashba effect, i.e. the spin-orbit splitting resulting from an electric field. In contrast to previous studies, where the carriers have usually been taken to be electrons, we focus on holes and are able to demonstrate remarkable improvements of the effect by several orders of magnitude. We also show that the frequently-neglected lattice-mismatch between GaAs and AlGaAs can be used to further enhance the efficiency of the wave vector splitting mechanism. The Rashba effect is the fundamental mechanism behind the Datta-Das spin transistor and we find that for a small electric field of 2 kV/cm the spin precession length becomes only 36nm.
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| 8. |
- Gvozdic, D. M., et al.
(författare)
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Superiority of p-type spin transistors
- 2006
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T126, s. 21-26
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Tidskriftsartikel (refereegranskat)abstract
- The spintronic device that has probably stimulated the most research interest is the Datta-Das spin transistor. The mechanism behind it, called the Rashba effect, is that an applied voltage gives rise to a spin splitting. We demonstrate that the relevant spin splitting in k-space can be made more than three orders of magnitude larger for holes than for electrons at the same electric field. This is partly achieved by utilizing the frequently neglected lattice-mismatch between GaAs and AlGaAs. We design heterostructures where this efficient Rashba effect should show up. Compared to present transistors, we conclude that electron-based spin transistors will have problems in becoming competitive but hole-based ones are much more promising.
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