58 research outputs found
Microwave-resonance-induced magnetooscillations and vanishing resistance states in multisubband two-dimensional electron systems
The dc magnetoconductivity of the multisubband two-dimensional electron
system formed on the liquid helium surface in the presence of resonant
microwave irradiation is described, and a new mechanism of the negative linear
response conductivity is studied using the self-consistent Born approximation.
Two kinds of scatterers (vapor atoms and capillary wave quanta) are considered.
Besides a conductivity modulation expected near the points, where the
excitation frequency for inter-subband transitions is commensurate with the
cyclotron frequency, a sign-changing correction to the linear conductivity is
shown to appear for usual quasi-elastic inter-subband scattering, if the
collision broadening of Landau levels is much smaller than thermal energy. The
decay heating of the electron system near the commensurability points leads to
magnetooscillations of electron temperature, which are shown to increase the
importance of the sign-changing correction. The line shape of
magnetoconductivity oscillations calculated for wide ranges of temperature and
magnetic field is in a good accordance with experimental observations.Comment: 13 pages, 8 figure
Photon-assisted scattering and magnetoconductivity oscillations in a strongly correlated 2D electron system formed on the surface of liquid helium
The influence of strong internal forces on photon-assisted scattering and on
the displacement mechanism of magnetoconductivity oscillations in a
two-dimensional (2D) electron gas is theoretically studied. The theory is
applied to the highly correlated system of surface electrons on liquid helium
under conditions that the microwave frequency is substantially different from
inter-subband resonance frequencies. A strong dependence of the amplitude of
magnetoconductivity oscillations on the electron density is established. The
possibility of experimental observation of such oscillations caused by
photon-assisted scattering is discussed.Comment: 7 pages, 1 figur
Photon-induced vanishing of magnetoconductance in 2D electrons on liquid He
We report on a novel transport phenomenon realized by optical pumping in
surface state electrons on helium subjected to perpendicular magnetic fields.
The electron dynamics is governed by the photon-induced excitation and
scattering-mediated transitions between electric subbands. In a range of
magnetic fields, we observe vanishing longitudinal conductivity sigma_xx. Our
result suggests the existence of radiation-induced zero-resistance states in
the nondegenerate 2D electron system.Comment: 4 pages, 5 figure
The fine structure of microwave-induced magneto-oscillations in photoconductivity of the two-dimensional electron system formed on a liquid-helium surface
The influence of the inelastic nature of electron scattering by surface
excitations of liquid helium (ripplons) on the shape of magnetoconductivity
oscillations induced by resonance microwave (MW) excitation is theoretically
studied. The MW field provides a substantial filling of the first excited
surface subband which sparks off inter-subband electron scattering by ripplons.
This scattering is the origin of magneto-oscillations in the momentum
relaxation rate. The inelastic effect becomes important when the energy of a
ripplon involved compares with the collision broadening of Landau levels.
Usually, such a condition is realized only at sufficiently high magnetic
fields. On the contrary, the inelastic nature of inter-subband scattering is
shown to be more important in a lower magnetic field range because of the new
enhancement factor: the ratio of the inter-subband transition frequency to the
cyclotron frequency. This inelastic effect affects strongly the shape of
conductivity oscillations which acquires an additional wavy feature (a mixture
of splitting and inversion) in the vicinity of the level-matching points where
the above noted ratio is close to an integer.Comment: 10 pages 6 figure
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