67 research outputs found
Microwave Photoconductivity in Two-Dimensional Electron Systems due to Photon-Assisted Interaction of Electrons with Leaky Interface Phonons
We calculate the contribution of the photon-assisted interaction of electrons
with leaky interface phonons to the dissipative dc photoconductivity of a
two-dimensional electron system in a magnetic field. The calculated
photoconductivity as a function of the frequency of microwave radiation and the
magnetic field exhibits pronounced oscillations. The obtained oscillation
structure is different from that in the case of photon-assisted interaction
with impurities. We demonstrate that at a sufficiently strong microwave
radiation in the certain ranges of its frequency (or in certain ranges of the
magnetic field) this mechanism can result in the absolute negative
conductivity.Comment: 3 pages, 1 figur
Giant microwave photoresistivity in a high-mobility quantum Hall system
We report the observation of a remarkably strong microwave photoresistivity
effect in a high-mobility two-dimensional electron system subject to a weak
magnetic field and low temperature. The effect manifests itself as a giant
microwave-induced resistivity peak which, in contrast to microwave-induced
resistance oscillations, appears only near the second harmonic of the cyclotron
resonance and only at sufficiently high microwave frequencies. Appearing in the
regime linear in microwave intensity, the peak can be more than an order of
magnitude stronger than the microwave-induced resistance oscillations and
cannot be explained by existing theories.Comment: 4 pages, 4 figure
Magnetoresistance Oscillations in Two-dimensional Electron Systems Induced by AC and DC Fields
We report on magnetotransport measurements in a high-mobility two-dimentional
electron system subject simultaneously to AC (microwave) and DC (Hall) fields.
We find that DC excitation affects microwave photoresistance in a nontrivial
way. Photoresistance maxima (minima) evolve into minima (maxima) and back,
reflecting strong coupling and interplay of AC- and DC-induced effects. Most of
our observations can be explained in terms of indirect electron transitions
using a new, ``combined'' resonant condition. Observed quenching of
microwave-induced zero resistance by a DC field cannot be unambiguously linked
to a domain model, at least until a systematic theory treating both excitation
types within a single framework is developed
Magnetoplasmon resonance in 2D electron system driven into a zero-resistance state
We report on a remarkably strong, and a rather sharp, photoresistance peak
originating from a dimensional magnetoplasmon resonance (MPR) in a high
mobility GaAs/AlGaAs quantum well driven by microwave radiation into a
zero-resistance state (ZRS). The analysis of the MPR signalreveals a negative
background providing experimental evidence for the concept of absolute negative
resistance associated with the ZRS. When a system is further subject to a dc
field, the maxima of microwave-induced resistance oscillations decay away and a
system reveals a state with close-to-zero differential resistance. The MPR
peak, on the other hand, remains essentially unchanged, indicating surprisingly
robust Ohmic behavior under the MPR conditions.Comment: 4 pages, 2 figures; to appear in Phys. Rev. B - Rapid Communication
Temperature Dependence of Microwave Photoresistance in 2D Electron Systems
We report on the temperature dependence of microwave-induced resistance
oscillations in high-mobility two-dimensional electron systems. We find that
the oscillation amplitude decays exponentially with increasing temperature, as
, where scales with the inverse magnetic field.
This observation indicates that the temperature dependence originates primarily
from the modification of the single particle lifetime, which we attribute to
electron-electron interaction effects.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Non-linear magnetotransport in microwave-illuminated two-dimensional electron systems
We study magnetoresistivity oscillations in a high-mobility two-dimensional
electron system subject to both microwave and dc electric fields. First, we
observe that the oscillation amplitude is a periodic function of the inverse
magnetic field and is strongly suppressed at microwave frequencies near
half-integers of the cyclotron frequency. Second, we obtain a complete set of
conditions for the differential resistivity extrema and saddle points. These
findings indicate the importance of scattering without microwave absorption and
a special role played by microwave-induced scattering events antiparallel to
the electric field.Comment: 4 pages, 4 figure
Resonant Phonon Scattering in Quantum Hall Systems Driven by dc Electric Fields
Using dc excitation to spatially tilt Landau levels, we study resonant
acoustic phonon scattering in two-dimensional electron systems. We observe that
dc electric field strongly modifies phonon resonances, transforming resistance
maxima into minima and back into maxima. Further, phonon resonances are
enhanced dramatically in the non-linear dc response and can be detected even at
low temperatures. Most of our observations can be explained in terms of
dc-induced (de)tuning of the resonant acoustic phonon scattering and its
interplay with intra-Landau level impurity scattering. Finally, we observe a
dc-induced zero-differential resistance state and a resistance maximum which
occurs when the electron drift velocity approaches the speed of sound.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
Features volitional qualities of adolescents involved in sports
The article presents an empirical study at studying the features of volitional qualities especially adolescents engaged and not engaged in sportsПредставлены результаты эмпирического исследования, направленного на изучение особенностей волевых качеств подростков, занимающихся и не занимающихся спорто
Symmetry breaking as the origin of zero-differential resistance states of a 2DEG in strong magnetic fields
Zero resistance differential states have been observed in two-dimensional
electron gases (2DEG) subject to a magnetic field and a strong dc current. In a
recent work we presented a model to describe the nonlinear transport regime of
this phenomenon. From the analysis of the differential resistivity and the
longitudinal voltage we predicted the formation of negative differential
resistivity states, although these states are known to be unstable. Based on
our model, we derive an analytical approximated expression for the
Voltage-Current characteristics, that captures the main elements of the
problem. The result allow us to construct an energy functional for the system.
In the zero temperature limit, the system presents a quantum phase transition,
with the control parameter given by the magnetic field. It is noted that above
a threshold value (), the symmetry is spontaneously broken. At
sufficiently high magnetic field and low temperature the model predicts a phase
with a non-vanishing permanent current; this is a novel phase that has not been
observed so far.Comment: 6 pages, 2 figure
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