共查询到17条相似文献,搜索用时 241 毫秒
1.
Spin-dependent electron transport of a waveguide with Rashba spin--orbit coupling in an electromagnetic field 下载免费PDF全文
We investigate theoretically the spin-dependent electron
transport in a straight waveguide with Rashba spin--orbit coupling
(SOC) under the irradiation of a transversely polarized
electromagnetic (EM) field. Spin-dependent electron conductance and
spin polarization are calculated as functions of the emitting
energy of electrons or the strength of the EM field by adopting the mode
matching approach. It is shown that the spin polarization can be
manipulated by external parameters when the strength of Rashba
SOC is strong. Furthermore, a sharp step structure is found to exist
in the total electron conductance. These results can be understood
by the nontrivial Rashba subbands intermixing and the electron
intersubband transition when a finite-range transversely polarized
EM field irradiates a straight waveguide. 相似文献
2.
Electron transport for a laser-irradiated quantum channel with Rashba spin--orbit coupling 下载免费PDF全文
We investigate theoretically the electron transport for a two-level
quantum channel (wire) with Rashba spin--orbit coupling under the
irradiation of a longitudinally-polarized external laser field at low
temperatures. Using the method of equation of motion for Keldysh
nonequilibrium Green function, we examine the time-averaged spin
polarized conductance for the system with photon polarization
parallel to the wire direction. By analytical analysis and a few
numerical examples, the interplay effects of the external laser field
and the Rashba spin--orbit coupling on the spin-polarized conductance
for the system are demonstrated and discussed. It is found that the
longitudinally-polarized laser field can adjust the spin polarization
rate and produce some photon sideband resonances of the conductance
for the system. 相似文献
3.
We study theoretically the electronic and transport property for an armchair-edge graphene nanoribbon (GNR.) with 12 and 11 transversal atomic lines, respectively. The ONR. is irradiated under an external longitudinal polarized high-frequency electromagnetic field at low temperatures. Within the framework of linear response theory in the perturbative regime, we examine the joint density of states and the real conductance of the system. It is demonstrated that, by numerical examples, some new photon-assisted intersubband transitions over a certain range of field frequency exist with different selection rules from those of both zigzag-edge GNR. and single-walled carbon nanotube. This opto-electron property dependence of armchair-edge GNR. on field frequency may be used to detect the high-frequency electromagnetic irradiation. 相似文献
4.
We have calculated the transport properties of electron through an
artificial quantum dot by using the numerical renormalization group
technique in this paper. We obtain the conductance for the system of
a quantum dot which is embedded in a one-dimensional chain in zero
and finite temperature cases. The external magnetic field gives rise
to a negative magnetoconductance in the zero temperature case. It
increases as the external magnetic field increases. We obtain the
relation between the coupling coefficient and conductance. If the
interaction is big enough to prevent conduction electrons from
tunnelling through the dot, the dispersion effect is dominant in this
case. In the Kondo temperature regime, we obtain the conductivity of
a quantum dot system with Kondo correlation. 相似文献
5.
Both the PIC (Particle-In-Cell) model and the Lie algebraic method can be used to simulate the transport of intense continuous beams. The PIC model is to calculate the space charge field, which is blended into the external field, and then simulate the trajectories of particles in the total field; the Lie algebraic method is to simulate the intense continuous beam transport with transport matrixes. Two simulation codes based on the two methods are developed respectively, and the simulated results of transport in a set of electrostatic lenses are compared. It is found that the results from the two codes are in agreement with each other, and both approaches have their own merits. 相似文献
6.
First-principles calculation of transport property in nano-devices under an external magnetic field 下载免费PDF全文
The mesoscopic quantum interference phenomenon (QIP) can be observed and behaves as the oscillation of conductance in nano-devices when the external magnetic field changes. Excluding the factor of impurities or defects, specific QIP is determined by the sample geometry. We have improved a first-principles method based on the matrix Green's function and the density functional theory to simulate the transport behaviour of such systems under a magnetic field. We have studied two kinds of QIP: universal conductance fluctuation (UCF) and Aharonov Bohm effect (A-B effect). We find that the amplitude of UCF is much smaller than the previous theoretical prediction. We have discussed the origin of difference and concluded that due to the failure of ergodic hypothesis, the ensemble statistics is not applicable, and the conductance fluctuation is determined by the flux-dependent density of states (DOSs). We have also studied the relation between the UCF and the structure of sample. For a specific structure, an atomic circle, the A-B effect is observed and the origin of the oscillation is also discussed. 相似文献
7.
The transport study of graphene based junctions has become one of the focuses in graphene research. There are two stacking configurations for monolayer–bilayer–monolayer graphene planar junctions. One is the two monolayer graphene contacting the same side of the bilayer graphene, and the other is the two-monolayer graphene contacting the different layers of the bilayer graphene. In this paper, according to the Landauer–Büttiker formula, we study the transport properties of these two configurations. The influences of the local gate potential in each part, the bias potential in bilayer graphene,the disorder and external magnetic field on conductance are obtained. We find the conductances of the two configurations can be manipulated by all of these effects. Especially, one can distinguish the two stacking configurations by introducing the bias potential into the bilayer graphene. The strong disorder and the external magnetic field will make the two stacking configurations indistinguishable in the transport experiment. 相似文献
8.
Molecular properties and potential energy function model of BH under external electric field 下载免费PDF全文
Using the density functional B3P86/cc-PV5Z method, the geometric structure of BH molecule under different external electric fields is optimized, and the bond lengths, dipole moments, vibration frequencies, and other physical properties parameters are obtained. On the basis of setting appropriate parameters, scanning single point energies are obtained by the same method and the potential energy curves under different external fields are also obtained. These results show that the physical property parameters and potential energy curves may change with external electric field, especially in the case of reverse direction electric field. The potential energy function without external electric field is fitted by Morse potential, and the fitting parameters are obtained which are in good agreement with experimental values. In order to obtain the critical dissociation electric parameter, the dipole approximation is adopted to construct a potential model fitting the corresponding potential energy curve of the external electric field. It is found that the fitted critical dissociation electric parameter is consistent with numerical calculation, so that the constructed model is reliable and accurate. These results will provide important theoretical and experimental reference for further studying the molecular spectrum, dynamics, and molecular cooling with Stark effect. 相似文献
9.
In this paper the mixing of a sample in the curved microchannel with heterogeneous
surface potentials is analysed numerically by using the control-volume-based finite
difference method. The rigorous models for describing the wall potential and
external potential are solved to get the distribution of wall potential and external
potential, then momentum equation is solved to get the fully developed flow field.
Finally the mass transport equation is solved to get the concentration field. The
results show that the curved microchannel has an optimized capability of sample
mixing and transport when the heterogeneous surface is located at the left
conjunction between the curved part and straight part. The variation of
heterogeneous surface potential $\psi_{\rm n}$has more influence on the capability
of sample mixing than on that of sample transport. The ratio of the curved
microchannel's radius to width has a comparable effect on the capability of sample
mixing and transport. The conclusions above are helpful to the optimization of the
design of microfluidic devices for the improvement of the efficiency of sample
mixing. 相似文献
10.
We study theoretically the low-temperature electronic transport property of a straight quantum wire under the irradiation of a finite-range transversely polarized external terahertz (THz) electromagnetic (EM) field. Using the freeelectron model and the scattering matrix approach, we show an unusual behaviour of the electronic transmission of this system. A sharp step-structure appears in the electronic transmission probability as the EM field strength increases to a threshold value when a coherent EM field is applied. We demonstrate that this effect physically comes from the inelastic scattering of electrons with lateral photons through intersubband transitions. 相似文献
11.
T. S. Li C. H. Lee M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(1):45-50
The transport properties of finite length double-walled carbon nanotubes subject to the influences of
a transverse electric field and a magnetic field with varying polar angles
are investigated theoretically. The electrical conductance, thermal conductance and Peltier coefficient
dependences on the external fields and symmetric configuration are studied in linear response regime.
Prominent peak structures of the electrical conductance are predicted when varying the electric field strength.
The features of the
conductance peaks are found to be strongly dependent on the external fields and
the intertube interactions.
The heights of the electrical and thermal conductance peaks display the quantized behavior,
while those of the Peltier coefficient do not. The conductance peaks are found to be broadened
by the finite temperature. 相似文献
12.
Spin and charge transport through a quantum dot coupled to external nonmagnetic leads is analyzed theoretically in terms of the non-equilibrium Green function formalism based on the equation of motion method. The dot is assumed to be subject to spin and charge bias, and the considerations are focused on the Kondo effect in spin and charge transport. It is shown that the differential spin conductance as a function of spin bias reveals a typical zero-bias Kondo anomaly which becomes split when either magnetic field or charge bias are applied. Significantly different behavior is found for mixed charge/spin conductance. The influence of electron-phonon coupling in the dot on tunneling current as well as on both spin and charge conductance is also analyzed. 相似文献
13.
K. Gnanasekar K. Navaneethakrishnan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):455-461
Spin-dependent Floquet scattering theory is developed to investigate the
photon-assisted spin-polarized electron transport through a semiconductor
heterostructure in the presence of an external electric field.
Spin-dependent Fano resonances and spin-polarized electron transport through
a laser irradiated time-periodic non-magnetic heterostructure in the
presence of Dresselhaus spin-orbit interaction and a gate-controlled Rashba
spin-orbit interaction are investigated. The electric field due to laser
along with the spin-orbit interactions help to get spin-dependent Fano
resonances in the conductance, whereas the external bias can be
appropriately adjusted to get a near 80% spin-polarized electron
transmission through heterostructures. The resultant nature of the Floquet
scattering depends on the relative strength of these two electric fields. 相似文献
14.
A charge-current switch manipulated by the macroscopic quantum coherence of a single-molecule magnet
B. Chang J.-Q. Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(4):515-522
We report a theoretical analysis of electron transport
through a quantum dot with an embedded biaxial single-molecule
magnet, which is coupled to ferromagnetic electrodes of parallel and
antiparallel magnet-configurations. For the antiparallel
configuration of complete polarization it is shown that the
originally prohibited electron transport can be opened up by the
macroscopic quantum coherence of the molecular magnet, which
provides a spin-flipping mechanism. The charge-current and
differential conductance are controllable by variation of the
magnitude and orientation of an external magnetic field, which in
turn manipulates the macroscopic quantum coherence of the molecular
magnet. Moreover, the transport can be switched off at particular
values of the magnetic field, where the tunnel splitting is quenched
by the quantum phase interference of tunnel paths.The transport
current and differential conductance as functions of the
electrode-polarization and magnetic field are extensively studied,
which may be useful in practical applications. A new transport
channel is found in the completely polarized parallel-configuration
induced by the tunnel splitting of molecular magnet and
resonance-peak splits of the conductance are observed in
non-completely polarized configurations. 75.50.Xx Molecular magnets 相似文献
15.
Shafranjuk SE 《J Phys Condens Matter》2011,23(49):495304
The electron transport through a carbon nanotube (CNT) double barrier junction exposed to an external electromagnetic field is studied. The electron spectrum in the quantum well (QW) formed by the junction bears relativistic features. We examine how the ac field affects the level quantization versus the ac field parameters and chirality. We find that the transport through the junction changes dramatically versus the ac field frequency and amplitude. These changes are pronounced in the junction's differential conductance, which allows judgment about the role of relativistic effects in the CNT QW structures. 相似文献
16.
C. A. Marlow A. Lfgren I. Shorubalko R. P. Taylor P. Omling L. Samuelson H. Linke 《Superlattices and Microstructures》2003,34(3-6):173
In linear response, the electric conductance of mesoscopic, two-terminal devices is symmetric with respect to the direction of an external magnetic field. The conductance symmetry, in general, breaks down in the non-linear regime of transport. Here we consider semiconductor quantum dots and show certain symmetries survive in the non-linear conductance with respect to the bias voltage and magnetic field that can be measured. 相似文献
17.
Kim J Kim JR Lee JO Park JW So HM Kim N Kang K Yoo KH Kim JJ 《Physical review letters》2003,90(16):166403
We report the observation of the resonant transport in multiwall carbon nanotubes in a crossed geometry. The resonant transport is manifested by an asymmetric peak in the differential conductance curve. The observed asymmetric conductance peak is well explained by the Fano resonance originating from the scattering at the contact region of the two nanotubes. The conductance peak depends sensitively on the external magnetic field and exhibits Aharonov-Bohm-type oscillation. 相似文献