12,711 research outputs found
Chasing 'Slow Light'
A critical review of experimental studies of the so-called 'slow light'
arising due to anomalously high steepness of the refractive index dispersion
under conditions of electromagnetically induced transparency or coherent
population oscillations is presented. It is shown that a considerable amount of
experimental evidence for observation of the 'slow light' is not related to the
low group velocity of light and can be easily interpreted in terms of a
standard model of interaction of light with a saturable absorber.Comment: 17 pages, 8 figures, to be published in June issue of Phisics:
Uspekhi under the title "Notes on Slow Light
Spin noise of itinerant fermions
We develop a theory of spin noise spectroscopy of itinerant, noninteracting,
spin-carrying fermions in different regimes of temperature and disorder. We use
kinetic equations for the density matrix in spin variables. We find a general
result with a clear physical interpretation, and discuss its dependence on
temperature, the size of the system, and applied magnetic field. We consider
two classes of experimental probes: 1. electron-spin-resonance (ESR)-type
measurements, in which the probe response to a uniform magnetization increases
linearly with the volume sampled, and 2. optical Kerr/Faraday rotation-type
measurements, in which the probe response to a uniform magnetization increases
linearly with the length of the light propagation in the sample, but is
independent of the cross section of the light beam. Our theory provides a
framework for interpreting recent experiments on atomic gases and conduction
electrons in semiconductors and provides a baseline for identifying the effects
of interactions on spin noise spectroscopy
High Bandwidth Atomic Magnetometery with Continuous Quantum Non-demolition Measurements
We describe an experimental study of spin-projection noise in a high
sensitivity alkali-metal magnetometer. We demonstrate a four-fold improvement
in the measurement bandwidth of the magnetometer using continuous quantum
non-demolition (QND) measurements. Operating in the scalar mode with a
measurement volume of 2 cm^3 we achieve magnetic field sensitivity of 22
fT/Hz^(1/2) and a bandwidth of 1.9 kHz with a spin polarization of only 1%. Our
experimental arrangement is naturally back-action evading and can be used to
realize sub-fT sensitivity with a highly polarized spin-squeezed atomic vapor.Comment: 4 page
Detection of radio frequency magnetic fields using nonlinear magneto-optical rotation
We describe a room-temperature alkali-metal atomic magnetometer for detection
of small, high frequency magnetic fields. The magnetometer operates by
detecting optical rotation due to the precession of an aligned ground state in
the presence of a small oscillating magnetic field. The resonance frequency of
the magnetometer can be adjusted to any desired value by tuning the bias
magnetic field. We demonstrate a sensitivity of in a 3.5 cm diameter, paraffin coated cell. Based
on detection at the photon shot-noise limit, we project a sensitivity of
.Comment: 6 pages, 6 figure
Spin noise in quantum dot ensembles
We study theoretically spin fluctuations of resident electrons or holes in
singly charged quantum dots. The effects of external magnetic field and
effective fields caused by the interaction of electron and nuclei spins are
analyzed. The fluctuations of spin Faraday, Kerr and ellipticity signals
revealing the spin noise of resident charge carriers are calculated for the
continuous wave probing at the singlet trion resonance.Comment: 8 pages, 4 figure
Optical measurements of spin noise as a high resolution spectroscopic tool
The intrinsic fluctuations of electron spins in semiconductors and atomic
vapors generate a small, randomly-varying "spin noise" that can be detected by
sensitive optical methods such as Faraday rotation. Recent studies have
demonstrated that the frequency, linewidth, and lineshape of this spin noise
directly reveals dynamical spin properties such as dephasing times, relaxation
mechanisms and g-factors without perturbing the spins away from equilibrium.
Here we demonstrate that spin noise measurements using wavelength-tunable probe
light forms the basis of a powerful and novel spectroscopic tool to provide
unique information that is fundamentally inaccessible via conventional linear
optics. In particular, the wavelength dependence of the detected spin noise
power can reveal homogeneous linewidths buried within inhomogeneously-broadened
optical spectra, and can resolve overlapping optical transitions belonging to
different spin systems. These new possibilities are explored both theoretically
and via experiments on spin systems in opposite limits of inhomogeneous
broadening (alkali atom vapors and semiconductor quantum dots).Comment: 4 pages, 4 figure
Skin effect with arbitrary specularity in Maxwellian plasma
The problem of skin effect with arbitrary specularity in maxwellian plasma
with specular--diffuse boundary conditions is solved. A new analytical method
is developed that makes it possible to to obtain a solution up to an arbitrary
degree of accuracy. The method is based on the idea of symmetric continuation
not only the electric field, but also electron distribution function. The
solution is obtained in a form of von Neumann series.Comment: 7 pages, 2 figure
Quantum, Multi-Body Effects and Nuclear Reaction Rates in Plasmas
Detailed calculations of the contribution from off-shell effects to the
quasiclassical tunneling of fusing particles are provided. It is shown that
these effects change the Gamow rates of certain nuclear reactions in dense
plasma by several orders of magnitude.Comment: 11 pages; change of content: added clarification of one of the
important steps in the derivatio
Noise spectroscopy and interlayer phase-coherence in bilayer quantum Hall systems
Bilayer quantum Hall systems develop strong interlayer phase-coherence when
the distance between layers is comparable to the typical distance between
electrons within a layer. The phase-coherent state has until now been
investigated primarily via transport measurements. We argue here that
interlayer current and charge-imbalance noise studies in these systems will be
able to address some of the key experimental questions. We show that the
characteristic frequency of current-noise is that of the zero wavevector
collective mode, which is sensitive to the degree of order in the system. Local
electric potential noise measured in a plane above the bilayer system on the
other hand is sensitive to finite-wavevector collective modes and hence to the
soft-magnetoroton picture of the order-disorder phase transition.Comment: 5 pages, 2 figure
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