6,467 research outputs found
Circular-Polarization-Dependent Study of Microwave-Induced Conductivity Oscillations in a Two-Dimensional Electron Gas on Liquid Helium
The polarization dependence of photoconductivity response at
cyclotron-resonance harmonics in a nondegenerate two-dimensional (2D) electron
system formed on the surface of liquid helium is studied using a setup in which
a circular polarization of opposite directions can be produced. Contrary to the
results of similar investigations reported for semiconductor 2D electron
systems, for electrons on liquid helium, a strong dependence of the amplitude
of magnetoconductivity oscillations on the direction of circular polarization
is observed. This observation is in accordance with theoretical models based on
photon-assisted scattering and, therefore, it solves a critical issue in the
dispute over the origin of microwave-induced conductivity oscillations.Comment: 5 pages, 4 figure
Coupling between Rydberg states and Landau levels of electrons trapped on liquid helium
We investigate the coupling between Rydberg states of electrons trapped on a
liquid Helium surface and Landau levels induced by a perpendicular magnetic
field. We show that this realises a prototype quantum system equivalent to an
atom in a cavity, where their coupling strength can be tuned by a parallel
magnetic field. We determine experimentally the renormalisation of the atomic
transition energies induced by the coupling to the cavity, which can be seen as
an analogue of the Lamb shift. When the coupling is sufficiently strong the
transition between the ground and first excited Rydberg states splits into two
resonances corresponding to dressed states with vacuum and one photon in the
cavity. Our results are in quantitative agreement with the energy shifts
predicted by the effective atom in a cavity model where all parameters are
known with high accuracy
Sliding of Electron Crystal of Finite Size on the Surface of Superfluid He-4 Confined in a Microchannel
We present a new study of the nonlinear transport of a two-dimensional
electron crystal on the surface of liquid helium confined in a 10
micrometer-wide channel in which the effective length of the crystal can be
varied from 10 to 215 micrometers. At low driving voltages, the moving electron
crystal is strongly coupled to deformation of the liquid surface arising from
resonant excitation of surface capillary waves, ripplons, while at higher
driving voltages the crystal decouples from the deformation. We find strong
dependence of the decoupling threshold of the driving electric field acting on
the electrons, on the size of the crystal. In particular, the threshold
electric field significantly decreases when the length of the crystal becomes
shorter than 25 micrometers. We explain this effect as arising from weakening
of surface deformations due to radiative loss of resonantly-excited ripplons
from an electron crystal of finite size, and we account for the observed effect
using an instructive analytical model.Comment: 5 figure
On Possible Measurement of Gravitational Interaction Parameters on Board a Satellite
The recently suggested SEE (Satellite Energy Exchange) method of measuring
the gravitational constant , possible equivalence principle violation
(measured by the E\"{o}tv\"{o}s parameter ) and the hypothetic 5th force
parameters and on board a drag-free Earth's satellite is
discussed and further developed. Various particle trajectories near a heavy
ball are numerically simulated. Some basic sources of error are analysed. The
measurement procedure is modelled by noise insertion to a ``true''
trajectory. It is concluded that the present knowledge of (for
m) and can be improved by at least two orders of
magnitude.Comment: (only two misprints on title page) 7 page
Dephasing of qubits by transverse low-frequency noise
We analyze the dissipative dynamics of a two-level quantum system subject to
low-frequency, e.g. 1/f noise, motivated by recent experiments with
superconducting quantum circuits. We show that the effect of transverse linear
coupling of the system to low-frequency noise is equivalent to that of
quadratic longitudinal coupling. We further find the decay law of quantum
coherent oscillations under the influence of both low- and high-frequency
fluctuations, in particular, for the case of comparable rates of relaxation and
pure dephasing
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