| 1. |
- Antonyuk, Vadim, et al.
(författare)
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Effect of electron-phonon interaction on electron conductance in one-dimensional systems
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 69:15
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the effect of electron-phonon interaction on the electronic transport in a one-dimensional wire where both electrons and phonons are quantum confined. We found substeps appeared in the quantized electron conductance, and the step height depends on the electron-phonon coupling strength. With increasing temperature, the substep structure smooths out. Dependent on the transmission probability through the wire, this substep correction can be either positive or negative. In the limiting cases we reproduce the existing results.
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| 2. |
- Antonyuk, Vadim, et al.
(författare)
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Phonon transmission in III-V semiconductor superlattices and alloys
- 2005
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 20:5, s. 347-352
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Tidskriftsartikel (refereegranskat)abstract
- We have used the transfer matrix approach to investigate the LA phonon transmission along the [0 0 1] growth direction in GaAs/GaAlAs superlattices and in Ga1-xAlxAs alloys. Our calculated minigap in the phonon dispersion induced by the zone folding matches reasonably to the phonon filtering experiment. However, in the regime of phonon ballistic transport, we found insignificant effect of zone folding on phonon thermal conductance. On the other hand, the alloy scatterings largely suppress the phonon transmission probability and so lower the phonon thermal conductance of alloys.
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| 3. |
- Chang, CH, et al.
(författare)
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Spin relaxation dynamics of quasiclassical electrons in ballistic quantum dots with strong spin-orbit coupling
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:24
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Tidskriftsartikel (refereegranskat)abstract
- We performed path integral simulations of spin evolution controlled by the Rashba spin-orbit interaction in the semiclassical regime for chaotic and regular quantum dots. The spin polarization dynamics have been found to be strikingly different from the D'yakonov-Perel' (DP) spin relaxation in bulk systems. Also an important distinction has been found between long time spin evolutions in classically chaotic and regular systems. In the former case the spin polarization relaxes to zero within relaxation time much larger than the DP relaxation, while in the latter case it evolves to a time independent residual value. The quantum mechanical analysis of the spin evolution based on the exact solution of the Schrodinger equation with Rashba SOI has confirmed the results of the classical simulations for the circular dot, which is expected to be valid in general regular systems. In contrast, the spin relaxation down to zero in chaotic dots contradicts what has to be expected from quantum mechanics. This signals on the importance of quantum effects missed in the semiclassical simulations for long time spin dynamics.
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| 4. |
- Chang, CH, et al.
(författare)
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Spin transmission through quantum dots with strong spin-orbit interaction
- 2004
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Ingår i: Physics Letters. Section A: General, Atomic and Solid State Physics. - : Elsevier BV. - 0375-9601. ; 326:5-6, s. 436-441
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Tidskriftsartikel (refereegranskat)abstract
- Quantum oscillations of the spin conductance through regular and chaotic 2D quantum dots under the varying Rashba spin-orbit interaction and at zero magnetic field have been investigated numerically by summing up the spin evolution matrices for classical transmitting trajectories. The Fourier analysis of these oscillations indicates a strong geometry dependence of the power spectra. The spectra for narrow rings are dominated by a single peak as previous analytic result, for regular quantum dots are represented by multiple peaks, and for chaotic quantum dots by quasi-continuum peaks.
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| 5. |
- Chao, Koung-An, et al.
(författare)
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Room-temperature semiconductor heterostructure refrigeration
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 87:2
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Tidskriftsartikel (refereegranskat)abstract
- With the proper design of semiconductor tunneling barrier structures, we can inject low-energy electrons via resonant tunneling, and take out high-energy electrons via a thermionic process. This is the operation principle of our semiconductor heterostructure refrigerator (SHR) without the need of applying a temperature gradient across the device. Even for the bad thermoelectric material AlGaAs, our calculation shows that at room temperature, the SHR can easily lower the temperature by 5 - 7 K. Such devices can be fabricated with the present semiconductor technology. Besides its use as a kitchen refrigerator, the SHR can efficiently cool microelectronic devices.
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| 6. |
- Chen, Weimin, et al.
(författare)
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Exciton spin relaxation in diluted magnetic semiconductor Zn1-xMnxSe/CdSe superlattices : Effect of spin splitting and role of longitudinal optical phonons
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:12
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Tidskriftsartikel (refereegranskat)abstract
- Exciton spin relaxation in diluted magnetic semiconductor (DMS) structures based on ZnMnSe is closely examined as a function of exciton spin splitting in an external magnetic field. A drastic increase in spin relaxation is observed when exciton spin splitting exceeds the longitudinal optical (LO) phonon energy. Direct experimental evidence has been provided from (1) spin injection from the DMS to an adjacent nonmagnetic quantum well that can be modulated by the LO-assisted spin relaxation and (2) hot exciton photoluminescence within the DMS where a spin flip is accompanied by the emission of one LO phonon.
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| 7. |
- Han, P, et al.
(författare)
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Analysis of optothermionic refrigeration based on semiconductor heterojunction
- 2006
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 99:7
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Tidskriftsartikel (refereegranskat)abstract
- We have examined the theory of optothermionic refrigeration combining the ideas of laser cooling and thermionic cooling [Mal'shukov and Chao, Phys. Rev. Lett. 86, 5570 (2001)] and its estimation on thermal energy extraction by using self-consistent calculations with the drift-diffusion model in this paper. Both the Auger and the Shockley-Read-Hall dissipation processes are considered. For GaAs/AlGaAs systems with various impurity concentrations and different widths of quantum well, it is found that the optothermionic cooler can extract thermal energy at a rate as much as 10 W/cm(2). The information to perform optothermionic refrigeration in real devices have also been provided. (c) 2006 American Institute of Physics.
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| 8. |
- Larsson, Marcus, et al.
(författare)
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Thermionic current reversal
- 2002
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Ingår i: Journal of Physics A: Mathematical and General. - 0305-4470. ; 35:35, s. 531-534
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Tidskriftsartikel (refereegranskat)abstract
- We have analysed the thermionic current over a potential barrier between a hot and a cold metallic wire, in the absence of an externally applied electric field. Because of the quantum nature of the transmission probability and the temperature behaviour of the Fermi distribution function, under proper conditions the thermionic electric current reverses its direction. However, the heat current remains in the same direction although its magnitude is suppressed.
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| 9. |
- Larsson, Magnus, et al.
(författare)
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Thermionic phenomena in a nanoscale ring without carrier reservoirs: A thermionic couple
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:23
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Tidskriftsartikel (refereegranskat)abstract
- We have studied various thermionic processes in a small one-dimensional ring consisting of a metallic wire and an insulator which serves as the potential barrier for the charge carriers in the metallic wire. The ring is not connected to any particle reservoir, but at the two junctions it is attached to two phonon reservoirs with different temperatures. The lengths of both the metallic wire and the insulating part are shorter than the carrier mean free path, and therefore the nonequilibrium electron distribution function was solved using the Boltzmann-equation approach with electron-phonon interaction at the two junctions. We found that there is always a heat current flowing from the hot junction to the cold one. The electric current over the potential barrier increases monotonically as the Fermi energy in the metallic wire approaches the potential barrier height from below. Using a modulation doped semiconductor ring for numerical calculation, the thermionic current is found to be almost linear with respect to the temperature difference between the two junctions. Consequently, our system can be developed into a nanometer scale thermionic couple.
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| 10. |
- Larsson, Marcus, et al.
(författare)
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Thermopower anomaly in multiple barrier structures
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:23: 233302
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Tidskriftsartikel (refereegranskat)abstract
- We have predicted that in suitable multiple barrier structures without applied bias, the thermopower may change sign because of quantum transport process. We have performed detailed numerical calculation to show that the predicted thermopower anomaly can be experimentally observed. This thermopower anomaly does not violate thermodynamic laws.
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| 11. |
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| 12. |
- Mal'shukov, AG, et al.
(författare)
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Optoelectric spin injection in semiconductor heterostructures without a ferromagnet
- 2002
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 65:24
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Tidskriftsartikel (refereegranskat)abstract
- We have shown that electron-spin density can be generated by a dc current flowing across a pn junction with an embedded asymmetric quantum well. Spin polarization is created in the quantum well by radiative electron-hole recombination when the conduction electron momentum distribution is shifted with respect to the momentum distribution of holes in the spin-split valence subbands. Spin current appears when the spin polarization is injected from the quantum well into the n-doped region of the pn junction. The accompanied emission of circularly polarized light from the quantum well can serve as a spin polarization detector.
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| 13. |
- Mal'shukov, AG, et al.
(författare)
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Spin-current generation and detection in the presence of an ac gate
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:23
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Tidskriftsartikel (refereegranskat)abstract
- We predict that in a narrow gap III-V semiconductor quantum well or quantum wire, an observable electron spin current can be generated with a time-dependent gate to modify the Rashba spin-orbit coupling constant. Methods to rectify the so generated ac current are discussed. An all-electric method of spin-current detection is suggested, which measures the voltage on the gate in the vicinity of a two-dimensional electron gas carrying a time-dependent spin current. Both the generation and detection do not involve any optical or magnetic mediator.
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| 14. |
- Mal'shukov, AG, et al.
(författare)
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Spin Hall conductivity of a disordered two-dimensional electron gas with Dresselhaus spin-orbit interaction
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 71:12
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Tidskriftsartikel (refereegranskat)abstract
- The spin Hall conductivity of a disordered two-dimensional electron gas has been investigated for a general spin-orbit interaction. We have found that in the diffusive regime of electron transport, the dc spin-Hall conductivity of a homogeneous system is zero due to impurity scattering when the spin-orbit coupling contains only the Rashba interaction, in agreement with existing results. However, when the Dresselhaus interaction is taken into account, the spin-Hall current is not zero. We also considered the spin-Hall currents induced by an inhomogeneous electric field. It is shown that a time-dependent electric charge induces a vortex of spin-Hall currents.
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| 15. |
- Mal'shukov, AG, et al.
(författare)
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Spin Hall effect on edge magnetization and electric conductance of a 2D semiconductor strip
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 95:14
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Tidskriftsartikel (refereegranskat)abstract
- The intrinsic spin Hall effect on spin accumulation and electric conductance in a diffusive regime of a 2D electron gas has been studied for a 2D strip of a finite width. It is shown that the spin polarization near the flanks of the strip, as well as the electric current in the longitudinal direction, exhibit damped oscillations as a function of the width and strength of the Dresselhaus spin-orbit interaction. Cubic terms of this interaction are crucial for spin accumulation near the edges. As expected, no effect on the spin accumulation and electric conductance have been found in case of Rashba spin-orbit interaction.
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| 16. |
- Mal'shukov, AG, et al.
(författare)
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Strain-induced coupling of spin current to nanomechanical oscillations
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 95:10
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Tidskriftsartikel (refereegranskat)abstract
- We propose a setup which allows us to couple the electron spin degree of freedom to the mechanical motions of a nanomechanical system not involving any of the ferromagnetic components. The proposed method employs the strain-induced spin-orbit interaction of electrons in narrow gap semiconductors. We have shown how this method can be used for detection and manipulation of the spin flow through a suspended rod in a nanomechanical device.
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| 17. |
- Tang, CS, et al.
(författare)
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Generation of spin current and polarization under dynamic gate control of spin-orbit interaction in low-dimensional semiconductor systems
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 71:19
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Tidskriftsartikel (refereegranskat)abstract
- Based on the Keldysh formalism, the Boltzmann kinetic equation and the drift-diffusion equation have been derived for studying spin-polarization flow and spin accumulation under effect of the time-dependent Rashba spin-orbit interaction in a semiconductor quantum well. The time-dependent Rashba interaction is provided by time-dependent electric gates of appropriate shapes. Several examples of spin manipulation by gates have been considered. Mechanisms and conditions for obtaining the stationary spin density and the induced rectified dc spin current are studied.
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