5,855 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
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
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
On the nonlinear NMR and magnon BEC in antiferromagnetic materials with coupled electron-nuclear spin precession
We present a new study of nonlinear NMR and Bose-Einstein Condensation (BEC)
of nuclear spin waves in antiferromagnetic MnCO3 with coupled electron and
nuclear spins. In particular, we show that the observed behaviour of NMR
signals strongly contradicts the conventional description of paramagnetic
ensembles of noninteracting spins based on the phenomenological Bloch
equations. We present a new theoretical description of the coupled
electron-nuclear spin precession, which takes into account an indirect
relaxation of nuclear spins via the electron subsystem. We show that the
magnitude of the nuclear magnetization is conserved for arbitrary large
excitation powers, which is drastically different from the conventional heating
scenario derived from the Bloch equations. This provides strong evidence that
the coherent precession of macroscopic nuclear magnetization observed
experimentally can be identified with BEC of nuclear spin waves with k=0.Comment: 12 pages, 8 figure
Features of the Coupled Nuclear–Electron Spin Precession in the Bose–Einstein Condensate of Magnons
The experimental detection of the Bose-Einstein condensate of magnons in coupled nuclear-electron spin precession in antiferromagnets brings the prospect of its use for magnonics and computer calculations. In particular, an attractive feature of such systems is a relatively large spin coherence time compared to traditional iron yttrium garnet samples. However, the observed Bose-Einstein condensation of magnons contradicts the Suhl-Nakamura model and the Bloch equations, which are usually used for these systems. The results of a direct experiment in antiferromagnetic MnCO3 performed in this work indicate that the Suhl-Nakamura model and the Bloch equations cannot adequately describe the coupled nuclear-electron spin motion at large levels of magnon excitation
Microwave absorption saturation and decay heating of surface electrons on liquid helium
The microwave (MW) resonance absorption and decay heating of surface electrons (SEs) on liquid ⁴He
are theoretically studied for the vapor atom scattering regime. The decay heating is shown to be an essential
occurrence of a MW resonance experiment appearing even at low excitation rates. It strongly affects the occupancies
of surface levels and the broadening of resonance lines long before the absorption suturation condition
is reached. Contrary to the model of cold SEs usually used for description of the MW resonance, the
new theory leads to MW absorption saturation when only a very small fraction of electrons (less than 10%) is
left on the ground and the first excited levels
Search for decay with VES detector
The isospin violating decay has been studied at
VES facility. This study is based at the statistics acquired in
interactions at 27, 36.6 and 41 GeV/c in diffractive reaction . The decay is observed. The ratio of
decay probabilities to is .Comment: 10 pages, 8 figures, presented at XII Conference on Hadron
Spectroscop
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