1,026 research outputs found
Crossover between distinct mechanisms of microwave photoresistance in bilayer systems
We report on temperature-dependent magnetoresistance measurements in balanced
double quantum wells exposed to microwave irradiation for various frequencies.
We have found that the resistance oscillations are described by the
microwave-induced modification of electron distribution function limited by
inelastic scattering (inelastic mechanism), up to a temperature of T*~4 K. With
increasing temperature, a strong deviation of the oscillation amplitudes from
the behavior predicted by this mechanism is observed, presumably indicating a
crossover to another mechanism of microwave photoresistance, with similar
frequency dependence. Our analysis shows that this deviation cannot be fully
understood in terms of contribution from the mechanisms discussed in theory.Comment: 7 pages, 4 figure
Nonlinear transport and oscillating magnetoresistance in double quantum wells
We study the evolution of low-temperature magnetoresistance in double quantum
wells in the region below 1 Tesla as the applied current density increases. A
flip of the magneto-intersubband oscillation peaks, which occurs as a result of
the current-induced inversion of the quantum component of resistivity, is
observed. We also see splitting of these peaks as another manifestation of
nonlinear behavior, specific for the two-subband electron systems. The
experimental results are quantitatively explained by the theory based on the
kinetic equation for the isotropic non-equilibrium part of electron
distribution function. The inelastic scattering time is determined from the
dependence of the inversion magnetic field on the current.Comment: 20 pages, 10 figure
Magnetoresistance oscillations in multilayer systems - triple quantum wells
Magnetoresistance of two-dimensional electron systems with several occupied
subbands oscillates owing to periodic modulation of the probability of
intersubband transitions by the quantizing magnetic field. In addition to
previous investigations of these magneto-intersubband (MIS) oscillations in
two-subband systems, we report on both experimental and theoretical studies of
such a phenomenon in three-subband systems realized in triple quantum wells. We
show that the presence of more than two subbands leads to a qualitatively
different MIS oscillation picture, described as a superposition of several
oscillating contributions. Under a continuous microwave irradiation, the
magnetoresistance of triple-well systems exhibits an interference of MIS
oscillations and microwaveinduced resistance oscillations. The theory
explaining these phenomena is presented in the general form, valid for an
arbitrary number of subbands. A comparison of theory and experiment allows us
to extract temperature dependence of quantum lifetime of electrons and to
confirm the applicability of the inelastic mechanism of microwave
photoresistance for the description of magnetotransport in multilayer systems.Comment: 10 pages, 5 figure
Thermally activated intersubband scattering and oscillating magnetoresistance in quantum wells
Experimental studies of magnetoresistance in high-mobility wide quantum wells
reveal oscillations which appear with an increase in temperature to 10 K and
whose period is close to that of Shubnikov-de Haas oscillations. The observed
phenomenon is identified as magnetointersubband oscillations caused by the
scattering of electrons between two occupied subbands and the third subband
which becomes occupied as a result of thermal activation. These small-period
oscillations are less sensitive to thermal suppression than the largeperiod
magnetointersubband oscillations caused by the scattering between the first and
the second subbands. Theoretical study, based on consideration of electron
scattering near the edge of the third subband, gives a reasonable explanation
of our experimental findings.Comment: 9 pages, 5 figure
Microwave zero-resistance states in a bilayer electron system
Magnetotransport measurements on a high-mobility electron bilayer system
formed in a wide GaAs quantum well reveal vanishing dissipative resistance
under continuous microwave irradiation. Profound zero-resistance states (ZRS)
appear even in the presence of additional intersubband scattering of electrons.
We study the dependence of photoresistance on frequency, microwave power. and
temperature. Experimental results are compared with a theory demonstrating that
the conditions for absolute negative resistivity correlate with the appearance
of ZRS.Comment: 5 pages, 4 figure
Моделирование пространственной неоднородности свободных носителей заряда в процедуре измерений их локальной концентрации
The paper presents results of the proposed generalized procedure in respect of measuring parameters of free charge carriers in the prescribed area of non-homogeneous object. It is shown that while solving measuring tasks on determination of their concentration non-homogeneous objects having boundaries between areas with various prevailing types of charge carriers can be modeled by division in body of interacting homogeneous areas. Realization of this model is executed by means of measuring procedure selection, identification of charge carrier type in the corresponding homogeneous area and taking measurements in accordance with the method which is based on the homogeneous object model.Представлены результаты разработки обобщенной процедуры измерений параметров свободных носителей заряда в заданной области неоднородного объекта. Показано, что неоднородные объекты, имеющие границы раздела областей с различными превалирующими типами носителей заряда, при решении измерительных задач определения их концентрации могут моделироваться разбиением на совокупность взаимодействующих однородных областей. Реализация этой модели осуществляется посредством операций выбора режима измерений, идентификации типа носителей заряда в соответствующей ему однородной области и выполнения измерений по методу, основанному на модели однородного объекта.
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