34,503 research outputs found
Photo-induced precession of magnetization in ferromagnetic (Ga,Mn)As
Precession of magnetization induced by pulsed optical excitation is observed
in a ferromagnetic semiconductor (Ga,Mn)As by time-resolved magneto-optical
measurements. It appears as complicated oscillations of polarization plane of
linearly-polarized probe pulses, but is reproduced by gyromagnetic theory
incorporating an impulsive change in an effective magnetic field due to changes
in magnetic anisotropy. It is inferred from the shape of the impulse that the
changes in anisotropy result from non-equilibrium carrier population: cooling
of hot photo-carriers and subsequent annihilation of photo-carriers
Pancharatnam and Berry Phases in Three-Level Photonic Systems
A theoretical analysis of Pancharatnam and Berry phases is made for biphoton
three-level systems, which are produced via frequency degenerate co-linear
spontaneous parametric down conversion (SPDC). The general theory of
Pancharatnam phases is discussed with a special emphasis on geodesic 'curves'in
Hilbert space. Explicit expressions for Pancharatnam, dynamical and geometrical
phases are derived for the transformations produced by linear phase-converters.
The problem of gauge invariance is treated along all the article
Current-feedback-stabilized laser system for quantum simulation experiments using Yb clock transition at 578 nm
We developed a laser system for the spectroscopy of the clock transition in
ytterbium (Yb) atoms at 578 nm based on an interference-filter stabilized
external-cavity diode laser (IFDL) emitting at 1156 nm. Owing to the improved
frequency-to-current response of the laser-diode chip and the less sensitivity
of the IFDL to mechanical perturbations, we succeeded in stabilizing the
frequency to a high-finesse ultra-low-expansion glass cavity with a simple
current feedback system. Using this laser system, we performed high-resolution
clock spectroscopy of Yb and found that the linewidth of the stabilized laser
was less than 320 Hz.Comment: 5 pages, 7 figure
Nonlinear behavior of geometric phases induced by photon pairs
In this study, we observe the nonlinear behavior of the two-photon geometric
phase for polarization states using time-correlated photons pairs. This phase
manifests as a shift of two-photon interference fringes. Under certain
arrangements, the geometric phase can vary nonlinearly and become very
sensitive to a change in the polarization state. Moreover, it is known that the
geometric phase for identically polarized photons is times larger than
that for one photon. Thus, the geometric phase for two photons can become two
times more sensitive to a state change. This high sensitivity to a change in
the polarization can be exploited for precision measurement of small
polarization variation. We evaluate the signal-to-noise ratio of the
measurement scheme using the nonlinear behavior of the geometric phase under
technical noise and highlight the practical advantages of this scheme.Comment: 10 pages, 10 figure
Large thermal Hall coefficient in bismuth
We present a systematical study of thermal Hall effect on a bismuth single
crystal by measuring resistivity, Hall coefficient, and thermal conductivity
under magnetic field, which shows a large thermal Hall coefficient comparable
to the largest one in a semiconductor HgSe. We discuss that this is mainly due
to a large mobility and a low thermal conductivity comparing theoretical
calculations, which will give a route for controlling heat current in
electronic devices.Comment: 4pages, 3 figure
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