14,063 research outputs found
Large spin relaxation rates in trapped submerged-shell atoms
Spin relaxation due to atom-atom collisions is measured for magnetically
trapped erbium and thulium atoms at a temperature near 500 mK. The rate
constants for Er-Er and Tm-Tm collisions are 3.0 times 10^-10 cm^3 s^-1 and 1.1
times 10^-10 cm^3 s^-1, respectively, 2-3 orders of magnitude larger than those
observed for highly magnetic S-state atoms. This is strong evidence for an
additional, dominant, spin relaxation mechanism, electrostatic anisotropy, in
collisions between these "submerged-shell" L > 0 atoms. These large spin
relaxation rates imply that evaporative cooling of these atoms in a magnetic
trap will be highly inefficient.Comment: 10 pages, 3 figure
Faraday-rotation fluctuation spectroscopy with static and oscillating magnetic fields
By Faraday-rotation fluctuation spectroscopy one measures the spin noise via
Faraday-induced fluctuations of the polarization plane of a laser transmitting
the sample. In the fist part of this paper, we present a theoretical model of
recent experiments on alkali gas vapors and semiconductors, done in the
presence of a {\em static} magnetic field. In a static field, the spin noise
shows a resonance line, revealing the Larmor frequency and the spin coherence
time of the electrons. Second, we discuss the possibility to use an {\em
oscillating} magnetic field in the Faraday setup. With an oscillating field
applied, one can observe multi-photon absorption processes in the spin noise.
Furthermore an oscillating field could also help to avoid line broadening due
to structural or chemical inhomogeneities in the sample, and thereby increase
the precision of the spin-coherence time measurement.Comment: 5 pages, 7 figure
GHz Spin Noise Spectroscopy in n-Doped Bulk GaAs
We advance spin noise spectroscopy to an ultrafast tool to resolve high
frequency spin dynamics in semiconductors. The optical non-demolition
experiment reveals the genuine origin of the inhomogeneous spin dephasing in
n-doped GaAs wafers at densities at the metal-to-insulator transition. The
measurements prove in conjunction with depth resolved spin noise measurements
that the broadening of the spin dephasing rate does not result from thermal
fluctuations or spin-phonon interaction, as previously suggested, but from
surface electron depletion
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
Noise spectroscopy of optical microcavity
The intensity noise spectrum of the light passed through an optical
microcavity is calculated with allowance for thermal fluctuations of its
thickness. The spectrum thus obtained reveals a peak at the frequency of
acoustic mode localized inside the microcavity and depends on the size of the
illuminated area. The estimates of the noise magnitude show that it can be
detected using the up-to-date noise spectroscopy technique.Comment: 10 pages, 1 figur
The Stabilization of Superconductivity by Magnetic Field in Out-of-Equilibrium Nanowires
A systematic study has been carried out on the previously reported
"magnetic-field-induced superconductivity" of Zn nanowires. By varying
parameters such as magnetic field orientation and wire length, the results
provide evidence that the phenomenon is a nonequilibrium effect associated with
the boundary electrodes. They also suggest there are two length scales
involved, the superconducting coherence length and quasiparticle relaxation
length. As wire lengths approach either of these length scales, the effect
weakens. We demonstrate that it is appropriate to consider the effect to be a
stabilization of superconductivity, that has been suppressed by an applied
current.Comment: (Updated Version) 9 pages, 8 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
Efficient Data Averaging for Spin Noise Spectroscopy in Semiconductors
Spin noise spectroscopy (SNS) is the perfect tool to investigate electron
spin dynamics in semiconductors at thermal equilibrium. We simulate SNS
measurements and show that ultrafast digitizers with low bit depth enable
sensitive, high bandwidth SNS in the presence of strong optical background shot
noise. The simulations reveal that optimized input load at the digitizer is
crucial for efficient spin noise detection while the bit depth influences the
sensitivity rather weakly
Simulations of magnetic and magnetoelastic properties of Tb2Ti2O7 in paramagnetic phase
Magnetic and magnetoelastic properties of terbium titanate pyrochlore in
paramagnetic phase are simulated. The magnetic field and temperature
dependences of magnetization and forced magnetostriction in Tb2Ti2O7 single
crystals and polycrystalline samples are calculated in the framework of
exchange charge model of crystal field theory and a mean field approximation.
The set of electron-deformation coupling constants has been determined.
Variations of elastic constants with temperature and applied magnetic field are
discussed. Additional strong softening of the crystal lattice at liquid helium
temperatures in the magnetic field directed along the rhombic symmetry axis is
predicted.Comment: 13 pages, 4 figures, 2 table
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
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