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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shauro V. P., Zobov V. E.
Заглавие : On the time-optimal implementation of quantum Fourier transform for qudits represented by quadrupole nucleus : Proceedings Paper
Коллективы : International Conference on Micro- and Nano-Electronics (Oct. 1-5, 2012; Zvenigorod, Russia)
Место публикации : Pros. SPIE: SPIE-Int. Soc. Optical Engineering, 2012. - Vol. 8700. - Ст.87001G. - ISSN 0277-786X, DOI 10.1117/12.2016983. - ISSN 978-0-8194-9487-0
Примечания : Cited References: 15
Предметные рубрики: ALGORITHMS
Ключевые слова (''Своб.индексиров.''): qudit--quantum fourier transform--time-optimal control--nuclear magnetic resonance
Аннотация: We consider the problem of time-optimal realization of the quantum Fourier transform gate for a single qudit with number of levels d from 3 to 8. As a qudit the quadrupole nucleus with spin I 1/2 controlled by NMR is considered. We calculate the dependencies of the gate error on the duration of radio-frequency pulse obtained by numerical optimization using Krotov-based algorithm. It is shown that the dependences of minimum time of QFT gate implementation on qudit dimension are different for integer and half-integer spins.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shauro V. P., Zobov V. E.
Заглавие : Global phase and minimum time of quantum Fourier transform for qudits represented by quadrupole nuclei
Место публикации : Phys. Rev. A: American Physical Society, 2013. - Vol. 88, Is. 4. - Ст.42320. - P. - ISSN 1050-2947, DOI 10.1103/PhysRevA.88.042320
Примечания : Cited References: 33
Предметные рубрики: ALGORITHMS
Аннотация: We demonstrate the relation between a global phase of the quantum gate and the layout of energy levels of its effective Hamiltonian required for implementing the gate for minimum time. By an example of the quantum Fourier transform gate for a qudit represented by a quadrupole nucleus with the spin I = 1, the effective Hamiltonians and minimum implementation times for different global phases are found. Using numerical optimal control methods, the problem of the global phase in searching for the optimal pulse shape is considered in detail for the quantum Fourier transform gate at I = 1, 3/2, 2, and 5/2. It is shown that at the constrained control time the gradient algorithms can converge to the solutions corresponding to different global phases or the same global phase with different minimum times of the gate implementation.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zabluda V. N., Varnakov S. N., Ovchinnikov S. G., Kosyrev N. N., Rishlicky S. V., Shvets V. A.
Заглавие : In-situ and in-time spectral magneto-ellipsometer : Abstract
Коллективы : "Functional Materials", International Conference , Taurida National V. I. Vernadsky University
Место публикации : Functional materials: Abstracts/ ed. V. N. Berzhansky. - Simferopol, 2013. - Ст.EP2-12P/3. - P.480. - ISBN 978-966-491-465-6
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Komogortsev S. V., Chizhik N. A., Filatov E. Yu., Korenev S. V., Shubin Yu.V., Velikanov D. A., Iskhakov R. S., Yurkin G.Yu.
Заглавие : Magnetic properties and L1 0 phase formation in CoPt nanoparticles
Коллективы : Moscow International Symposium on Magnetism
Место публикации : Diffusion and Defect Data Pt.B: Solid State Phenomena. - 2012. - Vol. 190. - P.159-162. - ISBN 1012-0394, DOI 10.4028/www.scientific.net/SSP.190.159. - ISBN 9783037854365
Ключевые слова (''Своб.индексиров.''): hard magnetic--magnetic anisotropy--magnetic nanoparticles--remnant magnetization--annealing time--copt nanoparticles--disorder-order--domain formation--hard magnetic--magnetic anisotropy energy--magnetic nanoparticles--phase formations--remnant magnetization--decomposition--magnetic anisotropy--magnetic materials--remanence--nanoparticles
Аннотация: The effect of the atomic disorder-order transformation on remanence, coercivity and magnetic anisotropy energy in CoPt nanoparticles prepared by thermal decomposition and annealed at 400oC for 4 and 16 hours has been studied. The observed remanence and magnetic anisotropy energy enhancement versus annealing time are discussed in the terms of ordering domain formation inside nanoparticles. В© (2012) Trans Tech Publications.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Shauro V. P., Zobov V. E., Shlegel N. V., Chimitova O. D., Atuchin V. V., Gavrilova T. A., Molokeev M. S., Bazarov B. G., Bazarova Zh.G.
Заглавие : On the time-optimal implementation of quantum Fourier transform for qudits represented by quadrupole nucleus
Коллективы : "Micro- and nanoelectronics – 2012", Int. Conf. (2012 ; окт. ; 1-5; Москва/ Звенигород, Россия)
Место публикации : International Conference "Micro- and nanoelectronics – 2012": Book of abstracts. - 2012. - Ст.q2-08. - P.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Tarasov I. A., Varnakov S. N., Yakovlev I. A., Zharkov S. M., Kosyrev N. N., Ovchinnikov S. G.
Заглавие : Time-resolved ellipsometric characterization of (Fe/Si)n multilayer film synthesis
Коллективы : Donostia International Conference on Nanoscaled Magnetism and Applications (9 -13 Sept. 2013; San Sebastian, Spain)
Место публикации : Donostia Int. Conf. on Nanoscaled Magnetism and Applications: Abstracts book. - 2013. - Ст.P1-27. - P.260
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sadreev A. F.
Заглавие : Feshbach projection formalism for transmission through a time-periodic potential
Место публикации : Phys. Rev. E: American Physical Society, 2012. - Vol. 86, Is. 5. - Ст.56211. - ISSN 1539-3755, DOI 10.1103/PhysRevE.86.056211
Примечания : Cited References: 33
Предметные рубрики: NUCLEAR REACTIONS
UNIFIED THEORY
QUANTUM
FIELD
SCATTERING
SYSTEM
STATES
Аннотация: The Feshbach projection formalism is applied to consider quantum transmission through a tight-binding wire subject to a time-periodic potential. The wire is coupled with two leads via the coupling constant v(C). The periodicity of the potential implies an additional temporal dimension that reduces the problem to stationary transmission through an effectively two-dimensional lattice system. The non-Hermitian effective Hamiltonian is formulated. Thist allows us to trace the redistribution of resonance positions and resonance widths with the growth of v(C) from the weak-coupling to the strong-coupling regime.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Shauro V. P.
Заглавие : Effect of a phase factor on the minimum time of a quantum gate
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2014. - Vol. 118, Is. 1. - P.18-26. - ISSN 1063-7761, DOI 10.1134/S106377611401021X. - ISSN 1090-6509
Примечания : Cited References: 42
Предметные рубрики: ALGORITHMS
Аннотация: A relationship between the phase factor of a quantum gate, the layout of energy levels of its effective Hamiltonian, and the implementation time of the gate is demonstrated. By an example of the direct and inverse quantum Fourier transforms (QFT) gates for a qutrit represented by a quadrupole nucleus with spin I = 1, as well as for a system of two qubits (I = 1/2), effective Hamiltonians and minimum implementation times corresponding to different global phases are obtained. Implementation schemes are proposed for these Hamiltonians by the nuclear magnetic resonance (NMR) technique with the use of sequences of radio-frequency (RF) pulses separated by intervals of free evolution. Analytic results for the minimum times of gates are in agreement with the results obtained by numerical optimization methods. The phase considered is divided into dynamic and geometric parts.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Tarasov I. A., Varnakov S. N., Yakovlev I. A., Zharkov S. M., Kosyrev N. N., Ovchinnikov S. G.
Заглавие : Time-resolved ellipsometric characterization of (Fe/Si)n multilayer film synthesis
Коллективы : Leibniz-Institut für Polymerforschung Dresden e. V., Workshop Ellipsometry (8; 2014 ; March 10-12; Dresden, Germany)
Место публикации : 8th Workshop Ellipsometry: Book of abstracts. - 2014. - P.81
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Arkhipkin V. G., Timofeev I. V.
Заглавие : Electromagnetically induced transparency and controlling the time shape of laser pulses
Место публикации : Dokl. Phys.: MAIK Nauka-Interperiodica / Springer, 2005. - Vol. 50, Is. 4. - P.165-168. - ISSN 1028-3358, DOI 10.1134/1.1922553
Примечания : Cited References: 14
Предметные рубрики: SPECTROSCOPY
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shauro V. P.
Заглавие : Exact solutions for time-optimal control of spin I=1 by NMR
Коллективы : Russian Foundation for Basic Research [14-07-31086]
Место публикации : Quantum Inf. Process.: Springer, 2015. - Vol. 14, Is. 7. - P.2345-2355. - ISSN 1570, DOI 10.1007/s11128-015-0999-8. - ISSN 15731332(eISSN)
Примечания : Cited References:34. - The author thanks V.E. Zobov for fruitful discussions. This study was supported by the Russian Foundation for Basic Research, Project No. 14-07-31086.
Предметные рубрики: QUANTUM COMPUTATION
SYSTEMS
Ключевые слова (''Своб.индексиров.''): quantum gate--qutrit--time-optimal control--nuclear magnetic resonance
Аннотация: We consider the problem of time-optimal control of quadrupole nucleus with the spin I = 1 by NMR. In contrast to the conventional methods based on selective pulses, the control is implemented using nonselective pulses separated by free-evolution intervals. Using the Cartan decomposition, the system of equations is obtained for finding parameters of a control field. Partial time-optimal solutions for the important single-qutrit gates (selective rotations and quantum Fourier transform) are found. The strong dependence of minimum gate implementation times on global phase of the gate is observed. The analytical values of minimum times are consistent with the numerical data.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pustovarov V. A., Ogorodnikov I. N., Omelkov S. I., Molokeev M. S., Kozlov A. V., Isaenko L. I.
Заглавие : Photoluminescence of monoclinic Li3AlF6 crystals under vacuum ultraviolet and soft X-ray excitations
Место публикации : Opt. Mater.: Elsevier, 2015. - Vol. 49. - P.201-207. - ISSN 0925-3467, DOI 10.1016/j.optmat.2015.09.011
Примечания : Cited References: 49. - This work was partly supported by the Ministry of Education and Science of the Russian Federation (the basic part of the government mandate); Center of Excellence "Radiation and Nuclear Technologies" (Competitiveness Enhancement Program of Ural Federal University, Russia), HASYLAB DESY (Projects Nos. 20110843, 20080119EC), European Social Fund ("Mobilitas" program, MJD219), Estonian Research Council (Institutional Research Funding IUT02-26) and Baltic Science Link project coordinated by the Swedish Research Council, VR
Предметные рубрики: LiBaAlF6 single-crystals
F-type centers
LiBaF3 crystals
Color-centers
Recombination luminescence
Rietveld refinement
VUV spectroscopy
Trapped excitons
Energy-transfer
Pure
Ключевые слова (''Своб.индексиров.''): li3alf6--time-resolved luminescence--vuv spectroscopy--defects
Аннотация: Using Bridgman technique we have grown monoclinic β-LiAF crystals suitable for optical studies, performed XRD-identification and Rietveld refinement of the crystal structure and carried out a photoluminescence study upon vacuum ultraviolet (VUV) and extreme ultraviolet (XUV)-excitations, using the low-temperature (T = 7.2 K) time-resolved VUV-spectroscopy technique. The intrinsic PL emission band at 340–350 nm has been identified as due to radiative recombination of self-trapped excitons. The electronic structure parameters were determined: bandgap E g ≈ 12.5 eV, energy threshold for creation of unrelaxed excitons 11.8 eV < E n < 12.5 eV . The PL emission bands at 320–325 and 450 nm were attributed to luminescence caused by lattice defects. We have discovered an efficient excitation of PL emission bands in the energy range of interband transitions ( E ex > 13.5 eV), as well as in the energy range of core transitions at 130 eV. We have revealed UV–VUV PL emission bands at 170 and 208 nm due to defects. A reasonable assumptions about the origin of the UV–VUV bands were discussed.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Decay of Multispin Multiple-Quantum Coherent States in the NMR of a Solid and the Stabilization of Their Intensity Profile with Time
Разночтения заглавия :авие SCOPUS: Decay of multispin multiple-quantum coherent states in the NMR of a solid and the stabilization of their intensity profile with time
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 6. - P1006-1014. - ISSN 1063-7761, DOI 10.1134/S1063776111140111
Примечания : Cited References: 27
Ключевые слова (''Своб.индексиров.''): cluster sizes--coherent state--decay rate--effective size--experimental data--intensity profiles--coherent light--decay (organic)--stabilization
Аннотация: Variations, experimentally observed in [14], in the intensity profiles of multiple-quantum (MQ) coherences in the presence of two special types of perturbations are explained on the basis of the theory, earlier developed by the authors, of the growth of the effective size of correlated clusters (the number of correlated spins) and the relaxation of MQ coherent states [23]. The intensity and the character of perturbation were controlled by the experimenters. It is shown that the observed stabilization of profiles with time is not associated with the stabilization of the cluster size. Quite the contrary, a cluster of correlated spins monotonically grows, while the observed variations in the intensity profile and its stabilization with time are attributed to the dependence of the decay rate of an MQ coherence on its order (its position in the MQ spectrum). The results of the theory are in good agreement with the experimental data.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pudlak M., Pichugin K. N., Nazmitdinov R. G., Pincak R.
Заглавие : Quantum nonequilibrium approach for fast electron transport in open systems: Photosynthetic reaction centers
Место публикации : Phys. Rev. E: AMER PHYSICAL SOC, 2011. - Vol. 84, Is. 5. - Ст.51912. - ISSN 1539-3755, DOI 10.1103/PhysRevE.84.051912
Примечания : Cited References: 34. - This work is partly supported by the Slovak Academy of Sciences in the framework of Center of Excellence NANOFLUID, VEGA Grants No. 2/0069/10, No. FIS2008-00781/FIS (Spain), and RFBR No. 11-02-00086 (Russia).
Предметные рубрики: BACTERIUM RHODOPSEUDOMONAS-VIRIDIS
PRIMARY CHARGE SEPARATION
AMINO-ACID-SEQUENCE
BACTERIOPHEOPHYTIN
RELAXATION
SUBUNIT
DONOR
MODEL
Ключевые слова (''Своб.индексиров.''): electron transfer--external fields--fast electron transport--initial conditions--non equilibrium--path-integral--perturbation theory--photosynthetic reaction center--second orders--time convolution--vibrational modes--electron transitions--perturbation techniques--quantum chemistry--photosynthesis
Аннотация: Creation of electrons or excitons by external fields in a system with initially statistically independent unrelaxed vibrational modes leads to an initial condition term. The contribution of this term in the time convolution generalized master-equation approach is studied in the second order of the perturbation theory in path-integral formalism. The developed approach, applied for the analysis of dynamics in the photosynthetic reaction center, exhibits the key role of the initial condition terms at the primary stage of electron transfer.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Shauro V. P.
Заглавие : On time-optimal NMR control of states of qutrits represented by quadrupole nuclei with the spin I=1
Разночтения заглавия :авие SCOPUS: On time-optimal NMR control of states of qutrits represented by quadrupole nuclei with the spin i = 1
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 2. - P181-191. - ISSN 1063-7761, DOI 10.1134/S1063776111060094
Примечания : Cited References: 48. - This work was supported by the Russian Foundation for Basic Research (project no. 09-07-00138) and the Dynasty Foundation.
Предметные рубрики: QUANTUM COMPUTATION
MAGNETIC-RESONANCE
ALGORITHMS
ELEMENTS
PULSES
DESIGN
QUDITS
GATES
Ключевые слова (''Своб.индексиров.''): logical operators--nuclear spins--numerical optimizations--optimality--physical parameters--quadrupole nuclei--qutrits--radio frequencies--rf pulse--three level systems--time dependence--time-optimal--computer control systems--computer simulation--fourier transforms--optimization--quantum computers--resonance--nuclear quadrupole resonance
Аннотация: Elementary logical operators (selective rotation, Fourier transform, controllable phase shift, and SUM gate) are considered for a quantum computer based on three-level systems (qutrits) represented by nuclear spins I = 1 under nuclear magnetic resonance conditions. The computer simulation of the realization of these operators by means of simple and composite selective radiofrequency (RF) pulses and optimized RF pulses is performed. The time dependence of the amplitude of last pulses is found by numerical optimization at different durations. Two variants are proposed for realization of a two-qutrit SUM gate by using one-qutrit or two-qutrit optimized RF pulses. The calculated time dependences of realization errors were used to study the time optimality of different methods for obtaining gates, proposed earlier and in this paper. The advantages and disadvantages of each of the methods are evaluated for different values of physical parameters.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Balaev D. A., Semenov S. V., Popkov S. I., Dubrovskiy A. A., Sapronova N. V., Volkov N. V.
Заглавие : Relaxation of low-temperature magnetoresistance and magnetization of polycrystalline (La0.5Eu0.5)(0.7)Pb0.3MnO3
Разночтения заглавия :авие SCOPUS: Relaxation of low-temperature magnetoresistance and magnetization of polycrystalline (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3
Место публикации : J. Phys. D. - 2011. - Vol. 44, Is. 25. - Ст.255001. - ISSN 0022-3727, DOI 10.1088/0022-3727/44/25/255001
Примечания : Cited References: 34. - This work was partially supported by the Lavrentyev Competition of the Young Scientist's Projects of the Siberian Branch of the Russian Academy of Sciences, Project No 12. The authors are grateful to A D Balaev and V M Sosnin for useful discussions on the results.
Предметные рубрики: INSULATOR-METAL TRANSITION
GRANULAR FILMS
NANOPARTICLES
PR0.7CA0.3MNO3
PERCOLATION
MANGANITES
Ключевые слова (''Своб.индексиров.''): antiferromagnetic boundaries--characteristic value--ferromagnetic domains--ferromagnetic metal--lanthanum manganites--logarithmic law--low temperatures--magneto-resistive effect--polycrystalline--relative orientation--relaxation of magnetization--temperature fluctuation--time evolutions--time interval--tunnel magnetoresistance--antiferromagnetism--electric resistance--europium--ferromagnetic materials--ferromagnetism--grain boundaries--grain size and shape--lanthanum compounds--lead--magnetic domains--magnetic moments--magnetoelectronics--magnetoresistance--manganese oxide--magnetization
Аннотация: Hysteresis and relaxation of magnetoresistance and magnetization of substituted (La0.5Eu0.5)(0.7)Pb0.3MnO3 lanthanum manganite in a low-temperature region ( 40 K) are investigated. It is shown that at these temperature features of the magnetoresistive effect are determined mainly by spin-dependent tunnelling of carriers via insulating grain boundaries. As was demonstrated previously, the grain boundaries may be antiferromagnetically ordered. Therefore, relaxation of magnetization and resistance is determined by the processes of relative orientation of the magnetic moments of ferromagnetic domains neighbouring the antiferromagnetic boundary of ferromagnetic domains under the action of temperature fluctuations. It is shown that relaxation follows the logarithmic law within the time interval t similar to 10(2)-3x10(3) s. A comparison between time evolutions of the magnetic moment and resistance shows that magnetoresistance and magnetization are related as delta R
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17.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Effect of intramolecular interaction on time growth of second moment of multiple quantum NMR in solids
Место публикации : INTERNATIONAL CONFERENCE ON RESONANCES IN CONDENSED MATTER: ALTSHULER100. Ser. Journal of Physics Conference Series: IOP PUBLISHING LTD, 2011. - Vol. 324: International Conference on Resonances in Condensed Matter (JUN 21-25, 2011, Kazan, RUSSIA). - Ст.12010. - ISBN 1742-6588, DOI 10.1088/1742-6596/324/1/012010
Примечания : Cited References: 12
Предметные рубрики: COHERENCES
DYNAMICS
Ключевые слова (''Своб.индексиров.''): dipole dipole interactions--double-quantum--intramolecular interactions--multiple quantum nmr--nuclear spin system--quantum spectrum--rate increase--second moments--solids containing methyl groups--time dependence--functional groups--quantum optics--solids--spin dynamics--hamiltonians
Аннотация: The time dependence of the NMR multiple quantum spectrum in solids containing methyl groups is investigated. We studied both of types of the nuclear spin systems: namely linking by secular part of the mutual dipole-dipole interaction and linking by effective double quantum Hamiltonian. It is revealed for the first type of systems the rate with the time of the growing up of the second moment when intramolecular interaction is present becomes less in compare with situation when a strong intramolecular interaction is absent. On the contrary for the second type of Hamiltonian the above rate increases.
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18.

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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19.

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 : Time relaxation of residual resistance of HTSC-based composites
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2007. - Vol. 460: 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (JUL 09-14, 2006, Dresden, GERMANY). - P1309-1310. - ISSN 0921-4534, DOI 10.1016/j.physc.2007.03.347
Примечания : Cited References: 5
Предметные рубрики: SUPERCONDUCTORS
Ключевые слова (''Своб.индексиров.''): granular htsc--resistance--relaxation--magnetic flux--granular htsc--magnetic flux--relaxation--resistance--copper oxides--crystallites--magnetic flux--magnetic relaxation--magnetization--yttrium barium copper oxides--anderson-like relaxation processes--flux trapping--residual resistance--time relaxation--josephson junction devices
Аннотация: Magnetoresistance curves R(H) and time relaxation of the residual resistance of bulk YBCO + CuO composites have been studied. These composites represent the network of Josephson junctions, where CuO acts as a barrier between YBCO grains. It has been shown that hysteresis of the R(H) dependences is related to the flux trapping within the YBCO crystallites. This flux induces magnetic field in the intergrain media. Time relaxation of the residual resistance is caused by relaxation of the magnetization of YBCO grains. The time dependence of the residual resistance obeys a logarithmic law, which describes the Anderson-like relaxation processes in the YBCO grains. (c) 2007 Elsevier B.V. All rights reserved.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sadreev A. F., Davlet-Kildeev K.
Заглавие : Electron transmission through an ac biased quantum point contact
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2007. - Vol. 75, Is. 23. - Ст.235309. - ISSN 1098-0121, DOI 10.1103/PhysRevB.75.235309
Примечания : Cited References: 41
Предметные рубрики: MULTIPROBE CONDUCTORS
BALLISTIC TRANSPORT
WIRES
GAS
CONSTRICTION
SCATTERING
TIME
QUANTIZATION
OSCILLATIONS
RESISTANCE
Аннотация: We consider a transmission through the potential relief created by a split gate constriction (quantum point contact). Simultaneously, dc and ac voltages V-up(t)=V-0+V-1 cos omega t and V-dw(t)=V-0+V-1 cos(omega t+theta) are applied to the gates. We show numerically that the in-phase ac voltages (theta=0) smear the conductance steps of the stationary conductance, while the antiphase ac voltages (theta=pi) only shift the conductance steps. Moreover, computation of currents in probing wires connected cross to the time-periodic quantum point contact reveals a net current for theta not equal 0,pi. This implies that the Schrodinger equation described by the electron transport under the effect of the time-periodic long electrodes is equivalent to the transmission in the crossed effective magnetic and electric fields, where the in-plane magnetic field b similar to theta is directed along the transport axis and the electric field e similar to omega is directed perpendicular to the plane of electron transport. Then the vector exb gives rise to the galvanomagnetic current directed cross to the electron transport.
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