共查询到20条相似文献,搜索用时 15 毫秒
1.
Patanè A Mori N Fowler D Eaves L Henini M Maude DK Hamaguchi C Airey R 《Physical review letters》2004,93(14):146801
We use a magnetic field applied along the axis of a semiconductor superlattice (SL) as a controllable means of creating a one-dimensional band structure. We demonstrate that the current flow through the SL is strongly suppressed when the electron motion perpendicular to the SL axis is strongly confined by the quantizing magnetic field. By modeling this behavior using semiclassical and nonequilibrium Green's function methods, we show that the observed quenching arises from a qualitative change in electron dynamics caused by increasing quantum confinement. 相似文献
2.
微带超晶格在磁场和太赫兹场调控下表现出丰富而复杂的动力学行为, 研究微带电子在外场作用下的输运性质对于太赫兹器件设计与研制具有重要意义. 本文采用准经典的运动方程描述了超晶格微带电子在沿超晶格生长方向(z方向)的THz场和相对于z轴倾斜的磁场共同作用下的非线性动力学特性. 研究表明, 在太赫兹场和倾斜磁场共同作用下, 超晶格微带电子随时间的演化表现出周期和混沌等新奇的运动状态. 采用庞加莱分支图详细研究了微带电子在磁场和太赫兹场调控下的运动规律, 给出了电子运行于周期和混沌运动状态的参数区间. 在电场和磁场作用下, 微带电子将产生布洛赫振荡和回旋振荡, 形成复杂的协同耦合振荡. 太赫兹场与这些协同振荡模式之间的相互作用是导致电子表现出周期态、混沌态以及倍周期分叉等现象的主要原因. 相似文献
3.
By analyzing biological rhythms obtained from finger tapping, we have investigated the differences of two biological rhythms between healthy and handicapped persons caused by Parkinson, brain infraction, car accident and so on. In this study, we have observed the motion of handedness of all subjects and obtained a slope a which characterizes a power-law relation between frequency and amplitude of finger-tapping rhythm. From our results, we have estimated that the slope a=0.06 is a rough criterion in order to distinguish healthy and handicapped persons. 相似文献
4.
D.P.A. Hardwick S.L. Naylor S. Bujkiewicz T.M. Fromhold D. Fowler A. Patan L. Eaves A.A. Krokhin P.B. Wilkinson M. Henini F.W. Sheard 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):285
We study the effects of inter-miniband electron tunneling and electric field domains on the current–voltage and conductance–voltage curves of biased semiconductor superlattices under the action of a magnetic field that is tilted relative to the plane of the layers. For this geometry, electrons in the superlattice minibands exhibit a unique type of stochastic semiclassical motion. At certain critical values of the electric field within the superlattice layers, the stochastic trajectories change abruptly from fully localized to completely unbounded, and map out an intricate web-like mesh of conduction channels in phase space. Delocalization of the electron paths produces a series of strong resonant peaks in the electron drift velocity versus electric field curves. We use these drift velocity characteristics to make self-consistent drift-diffusion calculations of the current–voltage and differential conductance–voltage curves of the superlattices, which reveal strong resonant features originating from the sudden delocalization of the stochastic single-electron paths. We show that this delocalization has a pronounced effect on the distribution of space charge and electric field domains within the superlattices. Inter-miniband tunneling greatly reduces the amount of space-charge buildup, thus enhancing the domain structure and both the strength and number of the current resonances. 相似文献
5.
《Superlattices and Microstructures》2000,27(5-6):495-498
We discuss electron transport through a semiconductor superlattice subject to an electric field parallel to, and a magnetic field perpendicular to, the growth axis using a semiclassical balance equation model. We find that the current–voltage characteristic becomes multistable in a large magnetic field; furthermore, hot electrons display novel features in their current–voltage characteristic, including absolute negative conductivity and a spontaneously generated dc current at zero bias. 相似文献
6.
A magnetic field parallel to the layers of a GaAs---GaAlAs superlattice leads to a quantisation of the subband dispersion relation. The discrete energy levels are calculated with a semiclassical quantisation scheme and it is shown that within the energy width of the subbands, closed orbits, and in the superlattice minigap open orbits, are formed. Experimentally this behaviour is observed as sharp peaks in the interband Landau level absorption for energies within the subband width (closed orbits) and the disappearance of these peaks at higher energies (where no closed orbits exist). 相似文献
7.
We report a novel electric field effect on angular dependent magnetotransport in quasi-one-dimensional layered conductors with a pair of sheetlike Fermi surfaces. Under tilted magnetic fields and additional interlayer electric fields, semiclassical electron orbits on two Fermi sheets become periodic at different magnetic field orientations. This causes double splitting of the Lebed's commensurability resonance in interlayer transport, and the amount of splitting allows us to estimate the Fermi velocity directly. We have successfully demonstrated this effect in the organic conductor alpha-(BEDT-TTF)2KHg(SCN)4. 相似文献
8.
A semiclassical method based on the closed-orbit theory is applied to
analysing the dynamics of photodetached electron of H$^- $ in the
parallel electric and magnetic fields. By simply varying the magnetic
field we reveal spatial bifurcations of electron orbits at a fixed
emission energy, which is referred to as the fold caustic in
classical motion. The quantum manifestations of these singularities
display a series of intermittent divergences in electronic flux
distributions. We introduce semiclassical uniform approximation to
repair the electron wavefunctions locally in a mixed phase space and
obtain reasonable results. The approximation provides a better
treatment of the problem. 相似文献
9.
A method to calculate the spectrum of the Lyapunov exponents for a periodic semiconductor nanostructure (superlattice) described in the framework of a semiclassical approach is proposed. The analysis of the stability of a stationary state in such a system is performed for autonomous dynamics and in the presence of a tilted magnetic field. The method of the Lyapunov exponents is used to study the effect of the tilted magnetic field on the stability of the stationary state and the characteristics of subterahertz oscillation regimes. 相似文献
10.
Homoclinic motion plays a key role in the organization of classical chaos in Hamiltonian systems. In this Letter, we show that it also imprints a clear signature in the corresponding quantum spectra. By numerically studying the fluctuations of the widths of wave functions localized along periodic orbits we reveal the existence of an oscillatory behavior that is explained solely in terms of the primary homoclinic motion. Furthermore, our results indicate that it survives the semiclassical limit. 相似文献
11.
We report the magnetoresistance of two-dimensional electron gas, which is made of GaAs based epitaxial mul-tilayers and laterally subjected to a periodic magnetic field. The modulation field is produced by an array of submicrometre ferromagnets fabricated at the surface of the heterostructure. The magnetoresistance of about 20% is found at low temperature 80K. The measurement is in quantitative agreement with semiclassical simulations, which reveal that the magnetoresistance is due to electrons trapped in snake orbits along lines of zero magnetic field. 相似文献
12.
A new method is proposed for fabricating polymer-coated silver hollow glass fibers to avoid the flexibility deterioration after the curing process. Transmission properties of fibers made by the two procedures with and without curing process are compared. Little difference was observed in the transmission properties at the wavelength 2.94 μm of Er:YAG laser light and 10.6 μm of CO2 laser light. The polymer layer is shown to be stable after 2-h, 5-W, continuous wave CO2 laser light transmission. 相似文献
13.
We calculate electronic states on a closed cylindrical surface as a model of a core-shell nanowire. The length of the cylinder can be infinite or finite. We define cardinal points on the circumference of the cylinder and consider a spatially uniform magnetic field perpendicular to the cylinder axis, in the direction South-North. The orbital motion of the electrons depends on the radial component of the field which is nonuniform around the circumference: it is equal to the total field at North and South, but vanishes at the West and East sides. For a strong field, when the magnetic length is comparable to the radius of the cylinder, the electronic states at North and South become localized cyclotron orbits, whereas at East and West the states become long and narrow snaking orbits propagating along the cylinder. The energy of the cyclotron states increases with the magnetic field whereas the energy of the snaking states is stable. Consequently, at high magnetic fields the electron density vanishes at North and South and concentrates at East and West. We include spin-orbit interaction with linear Rashba and Dresselhaus models. For a cylinder of finite length the Dresselhaus interaction produces an axial twist of the charge density relative to the center of the wire, which may be amplified in the presence of the Rashba interaction. 相似文献
14.
A. G. Balanov M. T. Greenaway A. A. Koronovskii O. I. Moskalenko A. O. Sel’skii T. M. Fromhold A. E. Khramov 《Journal of Experimental and Theoretical Physics》2012,114(5):836-840
The space-time dynamics of electron domains in a semiconductor superlattice is studied in a tilted magnetic field with regard to the effect of temperature. It is shown that an increase in temperature substantially changes the space-time dynamics of the system. This leads to a decrease in the frequency and amplitude of oscillations of a current flowing through the semiconductor superlattice. The quenching of oscillations is observed, which is attributed to the change in the drift velocity as a function of electric-field strength under the variation of temperature. 相似文献
15.
A. A. Abdujabbarov B. J. Ahmedov V. G. Kagramanova 《General Relativity and Gravitation》2008,40(12):2515-2532
The exact solution for the electromagnetic field occuring when the Kerr–Taub–NUT compact object is immersed (i) in an originally
uniform magnetic field aligned along the axis of axial symmetry (ii) in dipolar magnetic field generated by current loop has
been investigated. Effective potential of motion of charged test particle around Kerr–Taub–NUT gravitational source immersed
in magnetic field with different values of external magnetic field and NUT parameter has been also investigated. In both cases
presence of NUT parameter and magnetic field shifts stable circular orbits in the direction of the central gravitating object.
Finally we find analytical solutions of Maxwell equations in the external background spacetime of a slowly rotating magnetized
NUT star. The star is considered isolated and in vacuum, with monopolar configuration model for the stellar magnetic field. 相似文献
16.
A. Buchleitner K. Sacha D. Delande J. Zakrzewski 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):145-157
We present a semiclassical analysis of the dynamics of Rydberg states of atomic hydrogen driven by a resonant microwave field
of linear polarization. The semiclassical quasienergies of the atom in the field are found to be in very good agreement with
the exact quantum solutions. The ionization rates of individual eigenstates of the atom dressed by the field reflect their
quasiclassical dynamics along classical periodic orbits in the near integrable regime, but exhibit a transition to nonspecific
rates when global chaos takes over in phase space. We concentrate both on the principal resonance where the unperturbed Kepler
frequency is equal to the driving field frequency and on the higher primary resonance The latter case allows for the construction of nondispersive wave packets which propagate along Kepler ellipses of intermediate
eccentricity.
Received: 23 June 1998 / Accepted: 10 November
1998 相似文献
17.
P. M. Martin R. K. Hayden P. B. Wilkinson T. M. Fromhold C. R. Tench L. Eaves F. W. Sheard M. Henini N. Miura G. Hill 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
We use tunnel current spectroscopy to investigate the quantum states of two GaAs quantum wells coupled by a low (100 meV) (AlGa)As tunnel barrier. A high tilted magnetic field is used to generate strongly chaotic electron motion in the two wells which act as coupled chaotic ‘stadia'. The effect of the tunnel barrier on the dynamics of the system depends on the magnitude of the applied bias voltage V. For V375 mV, the central potential barrier acts as a perturbation which modifies the trajectories of selected periodic orbits in the quantum well. Scattering off the central barrier also generates new periodic orbits involving multiple collisions on all three barriers. These orbits ‘scar' distinct sets of eigenstates which generate periodic resonant peaks in the current–voltage characteristics of the device. When the device is biased such that the injected electrons just surmount the central barrier, our calculations reveal novel hybrid scarred states with both stable and chaotic characteristics. 相似文献
18.
We describe a new regime of magnetotransport in two-dimensional electron systems in the presence of a narrow potential barrier. In such systems, the Landau level states, which are confined to the barrier region in strong magnetic fields, undergo a deconfinement transition as the field is lowered. Transport measurements on a top-gated graphene device are presented. Shubnikov-de Haas (SdH) oscillations, observed in the unipolar regime, are found to abruptly disappear when the strength of the magnetic field is reduced below a certain critical value. This behavior is explained by a semiclassical analysis of the transformation of closed cyclotron orbits into open, deconfined trajectories. 相似文献
19.
20.
We study transport through a semiconductor superlattice with an electric field parallel to and a magnetic field perpendicular to the growth axis. Using a semiclassical balance equation model with elastic and inelastic scattering, we find that (1) the current-voltage characteristic becomes multistable in a large magnetic field and (2) "hot" electrons display novel features in their current-voltage characteristics, including absolute negative conductivity and a spontaneous dc current at zero bias. We discuss experimental situations providing hot electrons to observe these effects. 相似文献