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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Current-voltage characteristics of the resonant tunnelling double-barrier structure under time-periodical perturbation
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 1996. - Vol. 8, Is. 45. - P.8869-8887. - ISSN 0953-8984, DOI 10.1088/0953-8984/8/45/020
Примечания : Cited References: 38
Предметные рубрики: SEMICONDUCTOR DOUBLE-BARRIER
OSCILLATING QUANTUM-WELL
DEPENDENT TRANSPORT
INFRARED-RADIATION
TUNNELING TIMES
HETEROSTRUCTURES
TRANSMISSION
MODEL
FREQUENCIES
COHERENT
Аннотация: We consider a typical semiconductor resonant tunnelling GaAs/AlGaAs/GaAs nanostructure which forms a double-barrier potential with quasienergy levels corresponding to transition frequencies in the infrared and microwave regions. Two types of dynamical perturbation of the heterostructure in the form V-1(x, t) = V(1)x cos Omega t and V-2(t) = V-2 cos Omega t are considered. We analyse numerically a reconstruction of the electron transmission through the heterostructure and the current-voltage characteristics (IVC) under the influence of these dynamical perturbations. Both weak and strong perturbations are considered. We investigate the dependences of the transmission on the electron energy and the frequency of the external field with the main accent on the case where a frequency of the perturbation is tuned to a transition between quasienergies of the double-barrier structure. it is found that these resonant phenomena give rise to new peaks and dips in the IVC. In particular, it is shown that the dipole type of perturbation V-1(x, t) gives rise to a Rabi splitting of the transmission peaks and under certain conditions to a Rabi splining of the IVC peaks and dips. We demonstrate that dynamical perturbation may induce a direct current opposite to the direction of the applied voltage, and that this phenomenon takes the form of a sharp dip which has a resonant origin. It is observed that the dipole type of perturbation V-1(x, t) of laser radiation is more effective for tuning the IVC than the first perturbation V-2(t). Also absorption and emission of energy by an electron transmitted through the DBRTS are considered.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Berman G. P., Bulgakov E. N., Campbell D. K., Sadreev A. F.
Заглавие : Resonant tunneling in time-periodically modulated semiconductor nanostructures
Место публикации : Physica B. - 1996. - Vol. 225, Is. 1-2. - P.1-22. - ISSN 0921-4526, DOI 10.1016/0921-4526(96)00233-5
Примечания : Cited References: 39
Предметные рубрики: DOUBLE BARRIERS
TRANSMISSION
HETEROSTRUCTURES
Аннотация: We consider a semiconductor (AlGaAs/GaAs/AlGaAs) double-barrier resonant tunneling nanostructure (DBRTS), in which the bottom of the potential well is modulated by an external periodic potential V(t) = V-mod cos Omega t. We examine the resonance response to both mono-energetic and spatially localized incident electrons, extending previous results in three ways. First, we study numerically the resonant characteristics in the transmission probabilities as functions of both the electron's energy and the frequency of the external field. We find that new low-frequency resonant peaks appear in the frequency dependence of the transmission probabilities and discuss the origin and possible experimental observation of these peaks. Second, we develop an analytic perturbation theory (valid for small values of the parameter lambda = V-mod/h Omega) describing the processes of absorption and emission of single quanta of the modulation field and show that this perturbative treatment agrees well with the results of numerical calculations in the appropriate regions, up to and including the regime in which the one-quantum processes saturate. Third, for localized (Gaussian) incident wave packets, we show numerically that temporal modulations of the potential well in the DBRTS can induce spatial modulations in the transmitted and reflected wave packets. We develop a simple qualitative picture that explains our results. Finally, we estimate characteristic values of the parameters relevant for possible observation of these effects in laboratory experiments.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Alekseev K. N., Berman G. P., Campbell D. K.
Заглавие : Strange attractor in resonant tunneling
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 1998. - Vol. 58, Is. 7. - P3954-3962. - ISSN 0163-1829, DOI 10.1103/PhysRevB.58.3954
Примечания : Cited References: 38
Предметные рубрики: INTRINSIC BISTABILITY
RING CAVITY
OPTICAL TURBULENCE
TRANSMITTED LIGHT
QUANTUM-WELLS
OSCILLATIONS
BARRIERS
SYSTEM
STATE
TIME
Аннотация: We consider the process of resonant electron tunneling through a double-barrier potential, taking into account nonlinear dynamical effects generated by charge accumulation in the interbarrier space. We use the perturbation approach of Davydov and Ermakov, which was developed for investigating intrinsic bistability in resonant tunneling. For incoming electron flow, which is modulated slowly in time, we show that the resulting nonlinear dynamics can become chaotic, with the chaos described (because of the open nature of the system) by a strange attractor. We determine the conditions for the existence of this strange attractor and estimate characteristic experimental parameters for its observation.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fransson J., Eriksson O., Johansson B., Sandalov I. S.
Заглавие : On the non-orthogonality problem in the description of quantum devices
Коллективы : International Conference on Nonequilibrium Carrier Dynamics in Semiconductors
Место публикации : Physica B/ International Conference on Nonequilibrium Carrier Dynamics in Semiconductors (11 ; 1999 ; July ; 19-23 ; Kyoto, Japan). - 1999. - Vol. 272, Is. 1-4. - P.28-30. - ISSN 0921-4526, DOI 10.1016/S0921-4526(99)00343-9
Примечания : Cited References: 8
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): non-orthogonality--current--tunneling--correlation methods--electric contacts--electric currents--electron energy levels--electron tunneling--equations of motion--green's function--mathematical operators--matrix algebra--hubbard operators--potential barriers--tunneling currents--semiconductor quantum dots
Аннотация: An approach which allows to include the corrections from non-orthogonality of electron states in contacts and quantum dots is developed. Comparison of the energy levels and charge distributions of electrons in 1D quantum dot (QD) in equilibrium, obtained within orthogonal (OR) and non-orthogonal representations (NOR), with the exact ones shows that the NOR provides a considerable improvement, for levels below the top of barrier. The approach is extended to non-equilibrium states. A derivation of the tunneling current through a single potential barrier is performed using equations of motion for correlation functions. A formula for transient current derived by means of the diagram technique for Hubbard operators is given for the problem of QD with strongly correlated electrons interacting with electrons in contacts. The non-orthogonality renormalizes the tunneling matrix elements and spectral weights of Green functions. (C) 1999 Elsevier Science B.V. All rights reserved.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mendez-Bermudez J. A., Luna-Acosta G. A., Seba P., Pichugin K. N.
Заглавие : Understanding quantum scattering properties in terms of purely classical dynamics: Two-dimensional open chaotic billiards
Место публикации : Phys. Rev. E: AMER PHYSICAL SOC, 2002. - Vol. 66, Is. 4. - Ст.46207. - ISSN 1539-3755, DOI 10.1103/PhysRevE.66.046207
Примечания : Cited References: 34
Предметные рубрики: BALLISTIC-TRANSPORT
POINCARE SECTIONS
CAVITIES
EIGENFUNCTIONS
LOCALIZATION
CHANNEL
Ключевые слова (''Своб.индексиров.''): chaos theory--electron tunneling--laser applications--nonlinear systems--probability--waveguide components--chaotic motion--microlasers--quantum scattering--scattering probability--quantum theory--article
Аннотация: We study classical and quantum scattering properties of particles in the ballistic regime in two-dimensional chaotic billiards that are models of electron- or micro-waveguides. To this end we construct the purely classical counterparts of the scattering probability (SP) matrix \S(n,m)\(2) and Husimi distributions specializing to the case of mixed chaotic motion (incomplete horseshoe). Comparison between classical and quantum quantities allows us to discover the purely classical dynamical origin of certain general as well as particular features that appear in the quantum description of the system. On the other hand, at certain values of energy the tunneling of the wave function into classically forbidden regions produces striking differences between the classical and quantum quantities. A potential application of this phenomenon in the field of microlasers is discussed briefly. We also see the manifestation of whispering gallery orbits as a self-similar structure in the transmission part of the classical SP matrix.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fransson J., Holmstrom E., Eriksson O., Sandalov I.
Заглавие : Theory of spin filtering through quantum dots
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2003. - Vol. 67, Is. 20. - Ст.205310. - ISSN 1098-0121, DOI 10.1103/PhysRevB.67.205310
Примечания : Cited References: 28
Предметные рубрики: DEPENDENT TUNNELING JUNCTIONS
NARROW ENERGY BANDS
ELECTRON CORRELATIONS
MAGNETORESISTANCE
BARRIER
POLARIZATION
Аннотация: Using a nonequilibrium diagram technique for Hubbard operator Green functions combined with a generalization of the transfer Hamiltonian formalism, we calculate the transport through a magnetic quantum dot system with spin-dependent couplings to the contacts. In specific regimes of the parameter space the spin-dependent tunnel current becomes more than 99.95% spin polarized, suggesting that a device thus constructed can be used in spin-filter applications. First-principles electronic structure calculations show the existence of nanostructured systems, such as, e.g., MgO/Fe/Pd(5)/Fe/MgO (001), with the desired properties in the direction of the current.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Patrin G. S., Petrakovskii G. A., Sablina K. A., Ovchinnikov S. G., Varnakov S. N.
Заглавие : Tunneling magnetoresistance in a Eu0.7Pb0.3MnO3 (single crystal)-Fe (film) structure
Место публикации : Tech. Phys. Lett.: AMER INST PHYSICS, 2003. - Vol. 29, Is. 3. - P200-202. - ISSN 1063-7850, DOI 10.1134/1.1565633
Примечания : Cited References: 7
Аннотация: We have studied the magnetoresistive properties of a structure comprising single crystal manganite Eu0.7Pb0.3MnO3 covered with an epitaxial iron film. At temperatures below T-C of the manganite crystal, the structure exhibits positive magnetoresistance. The behavior of the resistance as a function of the magnetic field is characteristic of a tunneling junction with ferromagnetic electrodes separated by a thin insulating film. The observed effect is related to the formation of a transition layer at the manganite-Fe interface, which is depleted of oxygen and possesses dielectric properties. The sensitivity of the resistance with respect to the magnetic field is determined both by the negative magnetoresistance of the manganite crystal and by the tunneling contribution to the conductivity, whereby the tunneling current depends on the mutual orientation of magnetic moments of the electrodes (Eu0.7Pb0.3MnO3 crystal and Fe film). (C) 2003 MAIK "Nauka/Interperiodica".
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fransson J., Sandalov I., Eriksson O.
Заглавие : A perfect spin-filter quantum dot system
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2004. - Vol. 16, Is. 16. - P.L249-L254. - ISSN 0953-8984, DOI 10.1088/0953-8984/16/16/L03
Примечания : Cited References: 39
Предметные рубрики: NARROW ENERGY BANDS
ELECTRON CORRELATIONS
MAGNETIC-FIELD
MAGNETOTRANSPORT
CONDUCTANCE
RESISTANCE
BARRIER
FORMULA
VALVE
LIMIT
Ключевые слова (''Своб.индексиров.''): electric potential--electron tunneling--magnetic couplings--magnetic fields--magnetic filters--transport properties--electron correlations--magnetic contacts--source-drain voltage--spin projections--semiconductor quantum dots
Аннотация: The discovery of a novel effect in the transport through a QD spin-dependently coupled to magnetic contacts is reported. For a finite range of source-drain voltages the spin projections of the current cancel exactly, resulting in a completely suppressed output current. The spin down current behaves as one normally expects whereas the spin up current becomes negative. As the source-drain voltage is increased the spin up current eventually becomes positive. Thus, tuning the source-drain voltage such that the spin up current vanishes will result in a perfect spin filter.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Shaykhutdinov K. A., Popkov S. I., Petrov M. I.
Заглавие : Peculiarities of the time evolution of magnetoresistance of granular HTSC in a constant applied magnetic field
Коллективы :
Место публикации : Solid State Commun. - 2008. - Vol. 147, Is. 7-8. - P.284-287. - ISSN 0038-1098, DOI 10.1016/j.ssc.2008.05.044
Примечания : Cited References: 17. - This work was Supported by program "Quantum macrophysics" No. 3.4 of RAS and integration project No. 3.4 of SB RAS and in part by KSF, grant 18G011. D.A.B. and A.A.D. acknowledge the Russian Science Support Foundation.
Предметные рубрики: CRITICAL-STATE
SUPERCONDUCTORS
COMPOSITES
HYSTERESIS
RESISTANCE
Ключевые слова (''Своб.индексиров.''): superconductors--flux pinning and creep--tunneling--superconductors--flux pinning and creep--tunneling--agricultural products--carbon fiber reinforced plastics--copper oxides--electric conductivity--electric resistance--evolutionary algorithms--ferromagnetism--galvanomagnetic effects--grain (agricultural product)--health--hysteresis--magnetic devices--magnetic field effects--magnetic field measurement--magnetic fields--magnetic materials--magnetoelectronics--magnetoresistance--semiconductor metal boundaries--superconducting magnets--superconductivity--yttrium barium copper oxides--p ,p ,t measurements--applied (co)--applied magnetic fields--constant magnetic field (cmf)--elsevier (co)--evolution (co)--external fields--field induced--flux creep--hysteretic behavior--josephson couplings--low magnetic fields--magnetic (ce)--poly crystalline--superconducting grains--time evolutions--time relaxation--magnetism
Аннотация: The time evolution of the magnetoresistance of bulk YBCO + CuO composites at T = 4.2 K in constant applied magnetic fields was studied to clarify the mechanism of hysteretic behavior of magnetoresistance R(H) of granular HTSC. The composites represent "model" granular HTSC with weakened Josephson coupling between superconducting (YBCO) crystallites. It was found for the first time that on the ascending branch of R(H) dependence, the resistance at H = const decreased with time while on the descending branch, the resistance increased with time in ail applied constant magnetic field. In the range of low magnetic fields (below the minimum point of the descending branch of the R(H) dependence), the resistance at H const decreased again. Similar measurements performed oil pure polycrystalline YBCO at T = 77.4 K have shown that the behavior of evolution of resistance with time is similar to that observed for the composite. This proves the peculiarity of time evolution of maignetoresistance to be a common feature of granular HTSCs. The behavior revealed is well described by the model Of granular HTSC, where the intergrain media is in an effective magnetic field which is the superposition of the external field and the field induced by superconducting grains. The time evolution of resistance reflects the time relaxation of magnetization of HTSC grains due to the intragrain flux Creep Processes. (C) 2008 Elsevier Ltd. All rights reserved.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nesterov A. I., Ovchinnikov S. G.
Заглавие : Geometric phases and quantum phase transitions in open systems
Место публикации : Phys. Rev. E: AMER PHYSICAL SOC, 2008. - Vol. 78, Is. 1. - Ст.15202. - ISSN 1539-3755, DOI 10.1103/PhysRevE.78.015202
Примечания : Cited References: 29
Предметные рубрики: POINTS
DEGENERACIES
Ключевые слова (''Своб.индексиров.''): chlorine compounds--electron tunneling--ferromagnetism--ising model--magnetic fields--magnetism--open systems--quantum electronics--quantum optics--sedimentation--effective hamiltonian--eigenvalues--first orders--geometric phase--geometric phases--ground-state--hermitian--one-dimensional--open quantum systems--quantum phase transition--quantum phase transitions--transverse-magnetic fields--phase transitions
Аннотация: The relationship is established between quantum phase transitions and complex geometric phases for open quantum systems governed by a non-Hermitian effective Hamiltonian with accidental crossing of the eigenvalues. In particular, the geometric phase associated with the ground state of the one-dimensional dissipative Ising model in a transverse magnetic field is evaluated, and it is demonstrated that the related quantum phase transition is of the first order.
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