共查询到20条相似文献,搜索用时 15 毫秒
1.
B.K. Laurich D.L. Smith D.E. Watkins I. Sela S. Subbanna H. Kroemer 《Superlattices and Microstructures》1991,9(4)
We have investigated the nonlinear optical properties of a new class of strained-layer superlattices, the intrinsic Stark effect superlattices (ISES). The superlattices consisted of GaInAs/GaAs grown along the (211) B direction. We observed a shift of the excitonic absorotion to higher energies (blue shift) with increasing intensity of the transmitted beam. The observed optical nonlinearity was about one order of magnitude stronger than the one due to excitonic screening in the (100) oriented reference material. This effect is attributed to the screening of the internal electric fields by photogenerated carriers. 相似文献
2.
Transport and scattering in a lateral surface superlattice are investigated. A Monte Carlo calculation of the drift velocity versus electric field, using simple sinusoidal energy bands in two dimensions, shows negative differential mobility. The negative differential mobility is the result of Bloch oscillations, as is apparent from oscillations in the velocity autocorrelation function. 相似文献
3.
For a certain class of analytic potentialsV(x), matrix elements of the resolvent ofH
F = -d
2/dx
2 +Fx +V(x) with entire vectors of the translation group have meromorphic continuations from Imz>0 to the whole complex plane. The poles of these continuations are restricted to a discrete set independent of the analytic vectors chosen. Certain random potentials corresponding to an infinite number of particles distributed on the points of a Poisson set lie in this class with probability one as do a large class of periodic potentials.Supported by NSF Grant MCS 78-00101Supported by NSF Grant MCS 79-02490 相似文献
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We investigated the transport characteristics of Rabi oscillations, by using numerical methods, within a two-band tight-binding model driven by dc-ac electric fields. We found that Rabi oscillations make the long-time average current a sharply change, i.e. the current have resonant peaks appearing. Rabi oscillations are destroyed by dephasing; these peaks are the signatures of Rabi oscillations on the current response. The strong interband coupling will change the conditions of Rabi oscillations and, correspondingly, changes the places where the current resonant peaks appear. 相似文献
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Vl.A. Margulis S.V. Makarov T.V. Piterimova E.A. Gaiduk 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):153-164
Using a mean-field approximation, we have developed a systematic treatment of collective electronic modes in a semiconductor
superlattice (SL) in the presence of strong electric and magnetic fields parallel to the SL axis. The spectrum of collective
modes with zero wavevector along the SL axis is shown to consist of a principle magnetoplasmon mode and an infinite set of
Bernstein-like modes. For non-zero wavevector along the SL axis, in addition to the cyclotron modes, extra collective modes
are found at the frequencies |Nω
c±Mω
s|, which we call cyclotron-Stark modes (ω
c and ω
s are respectively the cyclotron and Stark frequencies, N and M are integer numbers). The frequencies of the modes propagating in “oblique” direction with respect to the SL axis show oscillatory
behavior as a function of electric field strength. All the modes considered have very weak spatial dispersion and they are
not Landau damped. The specific predictions made for the dispersion relations of the collective excitations should be observable
in resonant Raman scattering experiments.
Received 29 August 2002 / Received in final form 25 February 2003 Published online 4 June 2003
RID="a"
ID="a"e-mail: 612033@inbox.ru 相似文献
9.
Sonnino G 《Chaos (Woodbury, N.Y.)》2006,16(2):023115
A field theory approach to transport phenomena in magnetically confined plasmas is presented. The thermodynamic field theory (TFT), previously developed for treating the generic thermodynamic system out of equilibrium, is applied to plasmas physics. Transport phenomena are treated here as the effect of the field linking the thermodynamic forces with their conjugate flows combined with statistical mechanics. In particular, the Classical and the Pfirsch-Schluter regimes are analyzed by solving the thermodynamic field equations of the TFT in the weak-field approximation. We found that, the TFT does not correct the expressions of the ionic heat fluxes evaluated by the neoclassical theory in these two regimes. On the other hand, the fluxes of matter and electronic energy (heat flow) is further enhanced in the nonlinear Classical and Pfirsch-Schluter regimes. These results seem to be in line with the experimental observations. The complete set of the electronic and ionic transport equations in the nonlinear Banana regime, is also reported. A paper showing the comparison between our theoretic results and the experimental observations in the JET machine is currently in preparation. 相似文献
10.
F. Szmulowicz H.J. Haugan S. Elhamri G.J. Brown W.C. Mitchel 《Opto-Electronics Review》2010,18(3):267-270
We report on the results of transport studies of MBE-grown InAs/GaSb superlattices. We demonstrate that the in-plane mobility is limited by interface roughness scattering by showing that, as a function of InAs layer width L, the in-plane mobility behaves as μ ∝ L5.3, which closely follows the classic sixth power dependence expected from theory for interface-roughness-limited mobility. Fits to the mobility data indicate that, for one monolayer surface roughness, the roughness correlation length is about 35 Å. Next, we show that the in-plane carrier mobility in InAs/GaSb superlattices is inversely proportional to carrier density in n- and p-type samples, the result of screened interface roughness scattering. 相似文献
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《Superlattices and Microstructures》1999,25(5-6):819-828
We discuss some of the basic theoretical aspects of current-carrying states in superconducting superlattices with tunnel barriers in the mesoscopic regime, when p0 − 1 ⪡ a ⪡ ξ0(a is the superconducting layer thickness, p0is the Fermi momentum, ξ0is the BCS coherence length and ℏ = 1). We establish the necessary conditions for the observation of the classical Josephson effect (with sinusoidal current–phase dependence) and derive self-consistent analytical expressions for the critical Josephson current. These expressions are proportional to the small factor a / ξ0and have unusual temperature dependence as compared with the single-junction case. For certain parameter values, the superconducting gap exhibits an exponential decrease due to pair-breaking effect of the supercurrent. The supercurrent can completely destroy the superconductivity of the system above a certain characteristic temperature T * . In this paper, we also study the effect of intrabarrier exchange interactions. We show that this effect is strongly enhanced compared with the single-junction case and can manifest itself in an exponential decrease of the critical temperature. 相似文献
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Cabanillas-Gonzalez J Virgili T Gambetta A Lanzani G Anthopoulos TD de Leeuw DM 《Physical review letters》2006,96(10):106601
Subpicosecond photoinduced Stark spectroscopy experiments are carried out for measuring charge carrier mobility in organic semiconductors. The technique is demonstrated in state-of-art devices based on methanofullerene. The transient mobility of photogenerated charge carriers is measured in the picosecond time domain. Electric field dependent mobility is observed from the earliest time scales. In addition, two distinct transport regimes are revealed: a short-lived state, approximately 10 ps, of high mobility and a transient towards the trap limited transport, associated with the mesoscopic structure of the medium. 相似文献
15.
We describe linear and nonlinear transport across a strongly interacting single impurity Anderson model quantum dot with intermediate coupling to the leads, i.e. with tunnel coupling Γ of the order of the thermal energy k B T. The coupling is large enough that sequential tunneling processes (second order in the tunneling Hamiltonian) alone do not suffice to properly describe the transport characteristics. Upon applying a density matrix approach, the current is expressed in terms of rates obtained by considering a very small class of diagrams which dress the sequential tunneling processes by charge fluctuations. We call this the “dressed second order” (DSO) approximation. One advantage of the DSO is that, still in the Coulomb blockade regime, it can describe the crossover from thermally broadened to tunneling broadened conductance peaks. When the temperature is decreased even further (k B T < Γ), the DSO captures Kondesque behaviours of the Anderson quantum dot qualitatively: we find a zero bias anomaly of the differential conductance versus applied bias, an enhancement of the conductance with decreasing temperature as well as universality of the shape of the conductance as function of the temperature. We can without complications address the case of a spin degenerate level split energetically by a magnetic field. In case spin dependent chemical potentials are assumed and only one of the four chemical potentials is varied, the DSO yields in principle only one resonance. This seems to be in agreement with experiments with pseudo spin [U. Wilhelm, J. Schmid, J. Weis, K.V. Klitzing, Physica E 14, 385 (2002)]. Furthermore, we get qualitative agreement with experimental data showing a cross-over from the Kondo to the empty orbital regime. 相似文献
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We investigate the transport properties of a ladder with two random dimer (RD) chains. It is found that there are two extended states in the ladder with identical RD chains and a critical state regarded as an extended state in the ladder with pairing RD chains. Such a critical state is caused by the chiral symmetry. The ladder with identical RD chains can be decoupled into two isolated RD chains and the ladder with pairing RD chains can not. The analytic expressions of the extended states are presented for the ladder with identical RD chains. 相似文献
18.
Wei-Tao Lu Shun-Jin Wang Yong-Long Wang Hua Jiang Wen Li 《Physics letters. A》2013,377(19-20):1368-1372
We study the transmission of Dirac electrons through the one-dimensional periodic, Fibonacci, and Thue–Morse magnetic superlattices (MS), which can be realized by two different magnetic blocks arranged in certain sequences in graphene. The numerical results show that the transmission as a function of incident energy presents regular resonance splitting effect in periodic MS due to the split energy spectrum. For the quasiperiodic MS with more layers, they exhibit rich transmission patterns. In particular, the transmission in Fibonacci MS presents scaling property and fragmented behavior with self-similarity, while the transmission in Thue–Morse MS presents more perfect resonant peaks which are related to the completely transparent states. Furthermore, these interesting properties are robust against the profile of MS, but dependent on the magnetic structure parameters and the transverse wave vector. 相似文献
19.
Spizzo G Cappello S Cravotta A Escande DF Predebon I Marrelli L Martin P White RB 《Physical review letters》2006,96(2):025001
Magnetic field lines and the corresponding particle orbits are computed for a typical chaotic magnetic field provided by a magnetohydrodynamics numerical simulation of the reversed-field pinch. The m = 1 modes are phase locked and produce a toroidally localized bulging of the plasma which increases particle transport. The m = 0 and m = 1 modes produce magnetic chaos implying poor confinement. However, they also allow for the formation of magnetic islands which induce transport barriers inside the reversal surface. 相似文献
20.
We investigated transport in Nb-InAs hybrid structures in perpendicular magnetic fields up to the quantum Hall regime. Due
to the high contact quality of our samples, Andreev reflection dominates the transport properties in a range of experimental
parameters. Our experiments were performed on periodic arrays of Nb filled stripes or antidots in an InAs-based 2DEG. According
to geometry and field strength we observe the following effects: At low fields, up to a few flux quanta per unit cell, we
find phase-coherent behavior, such as flux-periodic oscillations. At slightly higher fields, the Andreev reflection probability
is determined by induced superconductivity in the 2DEG, which is gradually suppressed by an increasing magnetic field. In
the arrays of Nb filled antidots we find that the commensurability peaks are suppressed since Andreev reflection restores
regular motion in velocity space. Due to the high critical field of the Nb nanostructures, we can also enter the edge state
regime, where we observe a pronounced increase of the amplitude of 1/B-periodic magnetoresistance oscillations. The latter
can be traced to an enhanced backscattering of Andreev-reflected edge channels, which contain both electrons and holes.
PACS 74.45.+c; 73.43.Qt; 73.63.-b 相似文献