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[en] By employing non-equilibrium Green's function method, we calculated the spin transport through quantum dot (QD) embedded on AB ring with Rashba spin-orbit (SO) interaction and magnetic field. The results show that the spin polarization can be controlled by adjusting either SO interaction or the magnetic field applied on the QD. Furthermore, a new parameter (λ) is defined to describe the effect of magnetic field on SO coupling interaction. And it is found that the effect of SO coupling is suppressed with increasing the magnetic field
[en] Spin polarized transport was studied by employing non-equilibrium Green function method, for a model of quantum dot (QD) embedded in a mesoscopic Aharonov-Bohm (AB) ring with magnetic field applied on QD. In comparison with the situation without magnetic field on QD, the average spin occupations separate with the increase in applied magnetic field on QD; in addition, magnetic field on QD has profound effect on the density of states for different spins in QD; on the other hand, the amplitude and phase of transmission for up spin and down spin were found to present novel effects, such as, the additional peak in the phase of transmission. To understand the spin transport in the system of QD coupled to AB ring, the effects of the two magnetic fields imposed on the QD and penetrating the AB ring should be considered
[en] The transport properties of graphene/metal (Cu(111), Al(111), Ag(111), and Au(111)) planar junction are investigated using the first-principles nonequilibrium Green's function method. The planar junction induce second transmission minimum (TM2) below the Fermi level due to the existence of the Dirac point of clamped graphene. Interestingly, no matter the graphene is p- or n-type doped by the metal substrate, the TM2 always locates below the Fermi level. We find that the position of the TM2 is not only determined by the doping effect of metal lead on the graphene, but also influenced by the electrostatic potential of the metal substrate and the work function difference between the clamped and suspended graphene.
[en] Gallium nitride nanowires (GaN NWs) were synthesized by plasma-enhanced hot filament chemical vapor deposition under different ratios of nitrogen to hydrogen, which the GaN powder and nitrogen gas were used as the Ga and N sources. The characterization results indicate that the GaN NWs are grown in wurtzite crystalline structure with different length, diameters and surface adsorption. The field emission of GaN NWs was measured in the high vacuum condition of ∼10−6 Pa, which the results show that the turn-on field of GaN NWs changes from 0.86 to 2.8 V/μm depending on their structures and the current density can reach up to 830 μA/cm2 at the field of 6 V/μm. Combined the characterization results with the work function theory related to field emission, the origin of the field emission enhancement was analyzed, which associates with their surface potential and geometric structure. These results can enrich our knowledge on the field emission of GaN NWs and are highly related to the development of the next-generation of GaN nano-electronic devices.
[en] We study the spin-dependent electron transport in a special magnetic-electric superlattice periodically modulated by parallel ferromagnetic metal stripes and Schottky normal-metal stripes. The results show that, the spin-polarized current can be well controllable by modulating the magnetic strength of the ferromagnetic stripes or the voltage applied to the Schottky normal-metal stripes. It is obvious that, to the system of the magnetic superlattice, the polarized current can be enhanced by the magnetic strength of ferromagnetic stripes. Nevertheless, it is found that, for the magnetic-electric superlattice, the polarized current can also be remarkably advanced by the voltage applied to the Schottky normal-metal stripes. These results may indicate a useable approach for tunable spintronic devices
[en] By employing non-equilibrium Green's function method, the mesoscopic Fano effect modulated by Rashba spin-orbit (SO) coupling and external magnetic field has been elucidated for electron transport through a hybrid system composed of a quantum dot (QD) and an Aharonov-Bohm (AB) ring. The results show that the orientation of the Fano line shape is modulated by the Rashba spin-orbit interaction kRL variation, which reveals that the Fano parameter q will be extended to a complex number, although the system maintains time-reversal symmetry (TRS) under the Rashba SO interaction. Furthermore, it is shown that the modulation of the external magnetic field, which is applied not only inside the frame, but also on the QD, leads to the Fano resonance split due to Zeeman effect, which indicates that the hybrid is an ideal candidate for the spin readout device