4,574 research outputs found
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
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
Bistability and Hysteresis of Intersubband Absorption in Strongly Interacting Electrons on Liquid Helium
We study nonlinear inter-subband microwave absorption of electrons bound to
the liquid helium surface. Already for a comparatively low radiation intensity,
resonant absorption due to transitions between the two lowest subbands is
accompanied by electron overheating. The overheating results in a significant
population of higher subbands. The Coulomb interaction between electrons causes
a shift of the resonant frequency, which depends on the population of the
excited states and thus on the electron temperature . The latter is
determined experimentally from the electron photoconductivity. The
experimentally established relationship between the frequency shift and
is in reasonable agreement with the theory. The dependence of the shift on the
radiation intensity introduces nonlinearity into the rate of the inter-subband
absorption resulting in bistability and hysteresis of the resonant response.
The hysteresis of the response explains the behavior in the regime of frequency
modulation, which we observe for electrons on liquid He and which was
previously seen for electrons on liquid He
Transport properties of a quasi-1D Wigner Solid on liquid helium confined in a microchannel with periodic potential
We present transport measurements in a quasi-1D system of surface electrons
on liquid helium confined in a 101-m long and 5-m wide microchannel
where an electrostatic potential with periodicity of -m along the
channel is introduced. In particular, we investigate the influence of such a
potential on the nonlinear transport of quasi-1D Wigner Solid (WS) by varying
the amplitude of the periodic potential in a wide range. At zero and small
values of amplitude, quasi-1D WS in microchannel shows expected features such
as the Bragg-Cherenkov scattering of ripplons and reentrant melting. As the
amplitude of potential increases, the above features are strongly suppressed.
This behavior suggests loss of the long-range positional order in the electron
system, which is reminiscent of the re-entrant melting behaviour due to the
lateral confinement of WS in the channel
Unidirectional Charge Transport via Ripplonic Polarons in a Three-Terminal Microchannel Device
We study the transport of surface electrons on superfluid helium through a microchannel structure in which the charge flow splits into two branches, one flowing straight and one turned at 90°. According to Ohm’s law, an equal number of charges should flow into each branch. However, when the electrons are dressed by surface excitations (ripplons) to form polaronlike particles with sufficiently large effective mass, all the charge follows the straight path due to momentum conservation. This surface-wave induced transport is analogous to the motion of electrons coupled to surface acoustic waves in semiconductor 2DEGs
Photoresonance and conductivity of surface electrons on liquid ³He
Resonance variations of the in-plane conductivity of surface electrons (SEs) over liquid ³He induced by
microwave (MW) radiation of a fixed frequency are experimentally and theoretically studied for low temperature
scattering regimes (T < 0.5 K). The system was tuned to resonance by varying the amplitude of the
vertical electric field which shifts the positions of SE Rydberg levels. The line-shape change and reversing
of the sign of the effect are found to be opposite to that reported previously for weak vertical electric fields.
A theoretical analysis of conductivity of the SE system heated due to decay of electrons excited to the second
Rydberg level by the MW explains well the line-shape variations observed. It shows also that shifting
the MW resonance into the range of weak vertical fields leads to important qualitative changes in the
line-shape of SE conductivity which are in agreement with observations reported previously
Microwave Absorption of Surface-State Electrons on Liquid He
We have investigated the intersubband transitions of surface state electrons
(SSE) on liquid He induced by microwave radiation at temperatures from 1.1
K down to 0.01 K. Above 0.4 K, the transition linewidth is proportional to the
density of He vapor atoms. This proportionality is explained well by Ando's
theory, in which the linewidth is determined by the electron - vapor atom
scattering. However, the linewidth is larger than the calculation by a factor
of 2.1. This discrepancy strongly suggests that the theory underestimates the
electron - vapor atom scattering rate. At lower temperatures, the absorption
spectrum splits into several peaks. The multiple peak structure is partly
attributed to the spatial inhomogeneity of the static holding electric field
perpendicular to the electron sheet.Comment: 15 pages, 7 figures, submitted to J. Phys. Soc. Jp
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