1,266 research outputs found
Conserved Spin and Orbital Angular Momentum Hall Current in a Two-Dimensional Electron System with Rashba and Dresselhaus Spin-orbit Coupling
We study theoretically the spin and orbital angular momentum (OAM) Hall
effect in a high mobility two-dimensional electron system with Rashba and
Dresselhuas spin-orbit coupling by introducing both the spin and OAM torque
corrections, respectively, to the spin and OAM currents. We find that when both
bands are occupied, the spin Hall conductivity is still a constant (i.e.,
independent of the carrier density) which, however, has an opposite sign to the
previous value. The spin Hall conductivity in general would not be cancelled by
the OAM Hall conductivity. The OAM Hall conductivity is also independent of the
carrier density but depends on the strength ratio of the Rashba to Dresselhaus
spin-orbit coupling, suggesting that one can manipulate the total Hall current
through tuning the Rashba coupling by a gate voltage. We note that in a pure
Rashba system, though the spin Hall conductivity is exactly cancelled by the
OAM Hall conductivity due to the angular momentum conservation, the spin Hall
effect could still manifest itself as nonzero magnetization Hall current and
finite magnetization at the sample edges because the magnetic dipole moment
associated with the spin of an electron is twice as large as that of the OAM.
We also evaluate the electric field-induced OAM and discuss the origin of the
OAM Hall current. Finally, we find that the spin and OAM Hall conductivities
are closely related to the Berry vector (or gauge) potential.Comment: latest revised version; Accepted for publication in Physical Review
The impact of luteal phase support on endometrial estrogen and progesterone receptor expression: a randomized control trial
<p>Abstract</p> <p>Background</p> <p>To assess the impact of luteal phase support on the expression of estrogen receptor (ER) alpha and progesterone receptors B (PR-B) on the endometrium of oocyte donors undergoing controlled ovarian hyperstimulation (COH).</p> <p>Methods</p> <p>A prospective, randomized study was conducted in women undergoing controlled ovarian hyperstimulation for oocyte donation. Participants were randomized to receive no luteal support, vaginal progesterone alone, or vaginal progesterone plus orally administered 17 Beta estradiol. Endometrial biopsies were obtained at 4 time points in the luteal phase and evaluated by tissue microarray for expression of ER alpha and PR-B.</p> <p>Results</p> <p>One-hundred and eight endometrial tissue samples were obtained from 12 patients. No differences were found in expression of ER alpha and PR-B among all the specimens with the exception of one sample value.</p> <p>Conclusions</p> <p>The administration of progesterone during the luteal phase of COH for oocyte donor cycles, either with or without estrogen, does not significantly affect the endometrial expression of ER alpha and PR.</p
Microwave Components with MEMS Switches
RF MEMS switches with metal-metal contacts are being developed for microwave applications where broadband, high linearity performance is required. These switches provide less than 0.2 dB insertion loss through 40 GHz. This paper describes the integration of these switches into selected microwave components such as reconfigurable antenna elements, tunable filters, switched delay lines, and SPDT switches. Microwave and millimeter wave measured results from these circuits are presented
On the NLO Power Correction to Photon-Pion Transition Form Factor
We propose a perturbative evaluation for the next-to-leading-order (NLO)
power correction to the photon-pion transition form factor. The
effects of the NLO power correction are analyzed.Comment: 4 pages, 3 figures, Revtex, revised versio
Stochastic Lorentz forces on a point charge moving near the conducting plate
The influence of quantized electromagnetic fields on a nonrelativistic
charged particle moving near a conducting plate is studied. We give a
field-theoretic derivation of the nonlinear, non-Markovian Langevin equation of
the particle by the method of Feynman-Vernon influence functional. This
stochastic approach incorporates not only the stochastic noise manifested from
electromagnetic vacuum fluctuations, but also dissipation backreaction on a
charge in the form of the retarded Lorentz forces. Since the imposition of the
boundary is expected to anisotropically modify the effects of the fields on the
evolution of the particle, we consider the motion of a charge undergoing
small-amplitude oscillations in the direction either parallel or normal to the
plane boundary. Under the dipole approximation for nonrelativistic motion,
velocity fluctuations of the charge are found to grow linearly with time in the
early stage of the evolution at the rather different rate, revealing strong
anisotropic behavior. They are then asymptotically saturated as a result of the
fluctuation-dissipation relation, and the same saturated value is found for the
motion in both directions. The observational consequences are discussed. plane
boundary. Velocity fluctuations of the charge are found to grow linearly with
time in the early stage of the evolution at the rate given by the relaxation
constant, which turns out to be smaller in the parallel case than in the
perpendicular one in a similar configuration. Then, they are asymptotically
saturated as a result of the fluctuation-dissipation relation. For the
electron, the same saturated value is obtained for motion in both directions,
and is mainly determined by its oscillatory motion. Possible observational
consequences are discussed.Comment: 33 pages, 2 figure
Vero: A Method for Remotely Studying Human-AI Collaboration
Despite the recognized need in the IS community to prepare for a future of human-AI collaboration, the technical skills necessary to develop and deploy AI systems are considerable, making such research difficult to perform without specialized knowledge. To make human-AI collaboration research more accessible, we developed a novel experimental method that combines a video conferencing platform, controlled content, and Wizard of Oz methods to simulate a group interaction with an AI teammate. Through a case study, we demonstrate the flexibility and ease of deployment of this approach. We also provide evidence that the method creates a highly believable experience of interacting with an AI agent. By detailing this method, we hope that multidisciplinary researchers can replicate it to more easily answer questions that will inform the design and development of future human-AI collaboration technologies
ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions
We investigate ac Josephson effect in the resonant tunneling through
mesoscopic superconducting junctions. In the presence of microwave irradiation,
we show that the trajectory of multiple Andreev reflections can be closed by
emitting or absorbing photons. Consequently, photon-assisted Andreev states are
formed and play the role of carrying supercurrent. On the Shapiro steps, dc
component appears when the resonant level is near a series of positions with
spacing of half of the microwave frequency. Analytical result is derived in the
limit of infinite superconducting gap, based on which new features of ac
Josephson effect are revealed.Comment: 11 pages, 3 figure
Extraordinary Temperature Dependence of the Resonant Andreev Reflection
An extraordinary temperature dependence of the resonant Andreev reflection
via discrete energy level in a normal-metal / quantum-dot / superconductor
(N-QD-S) system is predicted theoretically by using Green function technique.
The width of zero bias conductance peak in N-QD-S is about and does not exhibit thermal broadening, where and
are the coupling strength between QD and leads. Considering the
intra-dot Coulomb interaction, the Coulomb blockade oscillations conducted by
Andreev reflection differs dramatically from that in N-QD-N. Instead of thermal
broadening, finite temperature induces more resonant peaks around the
oscillation peaks of zero temperature. This effect can be applied to determine
the coupling strength and QD level spacing in N-QD-S.Comment: 11 pages, 3 figures, LaTe
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