共查询到20条相似文献,搜索用时 15 毫秒
1.
M. R. Deshpande J. W. Sleight M. A. Reed R. G. Wheeler R. J. Matyi 《Superlattices and Microstructures》1996,20(4):513-522
Zeeman splitting of the ground state of single impurities in the quantum wells of resonant tunneling heterostructures is reported. We determine the absolute magnitude of the effective magnetic spin splitting factorg* for a single impurity in a 44 Å Al0.27Ga0.73As/GaAs/Al0.27Ga0.73As quantum well to be 0.28±0.02. This system also allows for independent measurement of the electron tunneling rates through the two potential barriers and estimation of the occupation probability of the impurity state in the quantum well. 相似文献
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J. ShenY.C. Tao 《Journal of magnetism and magnetic materials》2011,323(6):717-722
Combining an extended Julliere model with transfer matrix method, we study the spin-polarized resonant tunneling in GaMnAs/AlAs/GaAs/AlAs/GaMnAs double barrier ferromagnetic semiconductor (FS) tunnel junctions with the arbitrary angle θ between the magnetic directions of two FS's. It is shown that tunneling magnetoresistance (TMR) ratio linearly varies with sin2(θ/2). We also demonstrate that for the heavy and light holes, the properties of the spin-polarized resonant tunneling are obviously different. The present results are expected to be instructive for manufacturing the relevant semiconductor spintronic devices. 相似文献
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A. A. Shokri 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):475-481
Theoretical studies on spin-dependent transport in magnetic tunnel
heterostructures consisting of two diluted magnetic semiconductors
(DMS) separated by a nonmagnetic semiconductor (NMS) barrier, are
carried in the limit of coherent regime by including the effect of
angular dependence of the magnetizations in DMS. Based on
parabolic valence band effective mass approximation and
spontaneous magnetization of DMS electrodes, we obtain an
analytical expression of angular dependence of transmission for
DMS/NMS/DMS junctions. We also examine the dependence of spin
polarization and tunneling magnetoresistance (TMR) on barrier
thickness, temperature, applied voltage and the relative angle
between the magnetizations of two DMS layers in GaMnAs/GaAs/GaMnAs
heterostructures. We discuss the theoretical interpretation of
this variation. Our results show that TMR of more than 65% are
obtained at zero temperature, when one GaAs monolayer is used as a
tunnel barrier. It is also shown that the TMR decreases rapidly
with increasing barrier width and applied voltage; however at high
voltages and low thicknesses, the TMR first increases and then
decreases. Our calculations explain the main features of the
recent experimental observations and the application of the
predicted results may prove useful in designing nano spin-valve
devices. 相似文献
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Resonance splitting effect in multibarrier tunneling 总被引:1,自引:0,他引:1
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The use of cleaved, [111]-oriented monocrystalline InAs probe tips enables state-specific imaging in constant-current filled-state scanning tunneling microscopy. On Si(111)-(7 x 7), the adatom or rest-atom dangling-bond states can thus be mapped selectively at different tip-sample bias. This state-selective imaging is made possible by energy gaps in the projected bulk band structure of the semiconductor probe. The lack of extended bulk states in these gaps gives rise to efficient energy filtering of the tunneling current, to which only sample states not aligned with a gap contribute significantly. 相似文献
11.
Using the zero mode method, we compute the conductance of a wire consisting of a magnetic impurity coupled to two Luttinger liquid leads characterized by the Luttinger exponent alpha(>or=1). We find for resonance conditions, in which the Fermi energy of the leads is close to a single particle energy of the impurity, that the conductance as a function of temperature is G approximately equal (e(2)/h)(T/T(F))(2(alpha-2)), whereas for off-resonance conditions the conductance is G approximately equal (e(2)/h)(T/T(F))(2(alpha-1)). By applying either a gate voltage or a magnetic field or both, one of the spin components can be in resonance while the other is off resonance causing a strong asymmetry between the spin-up and spin-down conductances. 相似文献
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We discuss resonant tunneling through quantum dot energy levels considering the charging energy of the dot. The hamiltonian of the system is reduced to a form of the Anderson hamiltonian of resonant tunneling. The mean-field approximation is applied and current–voltage characteristics are evaluated. The self-consistent solution is investigated for the low tunneling rate case in the low-temperature condition. The current bistability and the related current hysteresis are pointed out. The Coulomb staircase is shown in the current–voltage characteristics. These features are all due to Coulomb repulsion within the dot. 相似文献
13.
R.M. Stevenson R.J. Young P. See D.G. Gevaux K. Cooper P. Atkinson I. Farrer D.A. Ritchie A.J. Shields 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):135
We demonstrate control of the fine-structure splitting of the exciton emission lines in single InAs quantum dots by the application of an in-plane magnetic field. The composition of the barrier material and the size and symmetry of the quantum dot are found to determine decrease or increase in the linear polarization splitting of the dominant exciton emission lines with increasing magnetic field. This enables the selection of dots for which the splitting can to be tuned to zero, within the resolution of our experiments. General differences in the g-factors and exchange splittings are found for different types of dot. 相似文献
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The possibility of semiconductor surface activation, which shows up as a long-term increase in the adsorption capacity in response to a short exposure to a pulsed magnetic field, is demonstrated for the first time. Magnetic-field-induced surface activation is studied on silicon, germanium, and gallium arsenide crystals. The effect revealed extends the capabilities of thin-film growth on the semiconductor surface. 相似文献
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We propose a theoretical scheme to determine the vacuum Rabi splitting in a single semiconductor quantum dot (SQD) induced by a metal nanoparticle (MNP). Based on cavity quantum electrodynamics, the exciton-plasmon interaction between the SQD and the MNP is considered while a strong pump laser and a weak probe laser are simultaneously presented. By decreasing the distance between them, we can increase the coupling strength. At resonance, thanks to the strong coupling, a vacuum Rabi splitting can be observed clearly in the probe absorption spectrum. The coupling strength can be obtained by measuring the vacuum Rabi splitting. This strong coupling is significant for the investigation of surface-plasmon-based quantum information processing. 相似文献
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Spectra of current oscillations caused by the transport of the electron domains induced by an applied voltage in a semiconductor superlattice with the absence and presence of the tilted magnetic field are numerically investigated with allowance for the interband tunneling. 相似文献
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The influence of strain on hole tunneling in trilayer and double barrier structures made of two diluted magnetic semiconductors (DMS) (Ga, Mn)As, separated by a thin layer of non-magnetic AlAs is investigated theoretically. The strain is caused by lattice mismatch as the whole structure is grown on a (In0.15Ga0.85)As buffer layer. The tensile strain makes the easy axis of magnetization orient along the growth direction. We found that biaxial strain has a strong influence on the tunneling current because the spin splitting at is comparable to the Fermi energy EF. Tensile strain decreases the tunneling magnetoresistance ratio. 相似文献
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W. Wulfhekel H.F. Ding W. Lutzke G. Steierl M. Vázquez P. Marín A. Hernando J. Kirschner 《Applied Physics A: Materials Science & Processing》2001,72(4):463-470
We give an overview over our recent efforts of high-resolution magnetic imaging using scanning tunneling microscopy with a
ferromagnetic tip. Magnetic sensitivity is obtained on the basis of local tunneling magnetoresistance between a soft magnetic
tip and the sample. The magnetisation of the tip is switched periodically with a small coil, leading to variations of the
tunneling current due to the tunneling magnetoresistance effect. These variations are detected with a lock-in amplifier to
separate spin-dependent parts from the topographic parts of the tunneling current such that the topography and the magnetic
structure of the sample can be recorded simultaneously. Crucial for this method is to avoid mechanical vibrations of the tip,
that may also lead to variations in the tunneling current. Exemplary studies of polycrystalline Ni and the closure domain
pattern of Co(0001) are presented, showing high contrast at acquisition times as low as 3 ms/pixel and a lateral resolution
of the order of 1 nm. Further it is demonstrated that besides topography and magnetisation, also local information about the
magnetic susceptibility can be obtained.
Received: 28 April 2000 / Accepted: 15 May 2000 / Published online: 7 March 2001 相似文献
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We present the first study relating structural parameters of precipitate-free Ge0.95Mn0.05 films to magnetization data. Nanometer-sized clusters--areas with increased Mn content on substitutional lattice sites compared to the host matrix--are detected in transmission electron microscopy analysis. The films show no overall spontaneous magnetization at all down to 2 K. The TEM and magnetization results are interpreted in terms of an assembly of superparamagnetic moments developing in the dense distribution of clusters. Each cluster individually turns ferromagnetic below an ordering temperature which depends on its volume and Mn content. 相似文献