Ballistic spin field-effect transistors: Multichannel effects

We study a ballistic spin field-effect transistor (SFET) with special attention to the issue of multi-channel effects. The conductance modulation of the SFET as a function of the Rashba spin-orbit coupling strength is numerically examined for the number of channels ranging from a few to close to 100. Even with the ideal spin injector and collector, the conductance modulation ratio, defined as the ratio between the maximum and minimum conductances, decays rapidly and approaches one with the increase of the channel number. It turns out that the decay is considerably faster when the Rashba spin-orbit coupling is larger. Effects of the electronic coherence are also examined in the multi-channel regime and it is found that the coherent Fabry-Perot-like interference in the multi-channel regime gives rise to a nested peak structure. For a nonideal spin injector/collector structure, which consists of a conventional metallic ferromagnet-thin insulator-2DEG heterostructure, the Rashba-coupling-induced conductance modulation is strongly affected by large resonance peaks that arise from the electron confinement effect of the insulators. Finally scattering effects are briefly addressed and it is found that in the weakly diffusive regime, the positions of the resonance peaks fluctuate, making the conductance modulation signal sample-dependent.Comment: 18 pages, 15 figure

Heightened Shareholder Interest in Firm Affairs following the Inception of Credit Default Swap Trade

The literature shows that a lender reduces its monitoring of client activities and decreases the accommodation it offers to a distressed client after the lender receives insurance on its outstanding client debt via a credit default swap (CDS). These changes in lender behavior can exacerbate downside risk but can also create upside potential for the reference firm’s shareholders. We predict that the firm’s shareholders, being the residual claimholders, would then increase their interest in firm affairs, by demanding improved corporate governance and the quality of financial reports. We find an increase in independence of the board of directors and a decline in the dual position of chief executive officer and board chairman following the onset of CDS trading. We also find higher earnings response coefficient and trading volumes around the earnings announcement dates and lower post–earnings announcement drift. Overall, our results suggest that shareholders demand and obtain higher quality of, or pay greater attention to, financial reports in the years following the onset of CDS trading

Managerial incentives and changes in corporate investments following the inception of credit default swap trade

A credit default swap (CDS) enables a lender to hedge its risk exposure on a loan given to reference client. The lender then reduces the monitoring of the client’s activities as well as aiding the distressed client. Two contrasting predictions can be made about how the borrower would respond to the altered lender-borrower relationship. (1) The borrower reduces risky investments to lower its vulnerability to financial distress. (2) The borrower pursues volatility-enhancing projects to increase the value of call options built into its shareholder investments. We find that a borrower shifts to a more conservative policy when its managers have low portfolio sensitivity to stock volatility (vega). A borrower with high managerial vega, however, seeks volatility-enhancing projects. Shareholders then increase vega incentives for managers to maintain investments in risky, positive NPV projects at pre CDS levels. This action, however, also results in higher bankruptcy risk. Our study shows a unique interaction between the manager-shareholder and lender-shareholder conflicts arising from CDS inception, which alters the course of the borrower’s operating policy

Radiative neutron capture on a proton at BBN energies

The total cross section for radiative neutron capture on a proton, $np \to d \gamma$, is evaluated at big bang nucleosynthesis (BBN) energies. The electromagnetic transition amplitudes are calculated up to next-to leading order within the framework of pionless effective field theory with dibaryon fields. We also calculate the $d\gamma\to np$ cross section and the photon analyzing power for the $d\vec{\gamma}\to np$ process from the amplitudes. The values of low energy constants that appear in the amplitudes are estimated by a Markov Chain Monte Carlo analysis using the relevant low energy experimental data. Our result agrees well with those of other theoretical calculations except for the $np\to d\gamma$ cross section at some energies estimated by an R-matrix analysis. We also study the uncertainties in our estimation of the $np\to d\gamma$ cross section at relevant BBN energies and find that the estimated cross section is reliable to within $\sim$1% error.Comment: 21 pages and 12 eps figures; 6 eps figures and 2 references added, and accepted for publication in Phys. Rev.

Microscopic Theory of Rashba Interaction in Magnetic Metal

Theory of Rashba spin-orbit coupling in magnetic metals is worked out from microscopic Hamiltonian describing d-orbitals. When structural inversion symmetry is broken, electron hopping between $d$-orbitals generates chiral ordering of orbital angular momentum, which combines with atomic spin-orbit coupling to result in the Rashba interaction. Rashba parameter characterizing the interaction is band-specific, even reversing its sign from band to band. Large enhancement of the Rashba parameter found in recent experiments is attributed to the orbital mixing of 3d magnetic atoms with non-magnetic heavy elements as we demonstrate by first-principles and tight-binding calculations.Comment: 5 pages, 2 figure

Animal Assisted Intervention for Rehabilitation Therapy and Psychotherapy

Animal-assisted Intervention (AAI) is a goal-oriented intervention that intentionally includes or incorporates animals in health, education, and human service for the purpose of therapeutic gains in humans. AAI incorporates human-animal teams in formal human service such as Animal-assisted Therapy (AAT) or Animal-assisted Education (AAE). Animal-assisted Activity (AAA) is the informal AAI often conducted on a volunteer basis by the human-animal team for motivational, educational, and recreational purposes. AAI could be used for rehabilitation therapy and psychotherapy for patients with various symptoms. AAI uses animals, mostly dogs, to aid in healing patients holistically. Dogs have an overwhelming gratitude and exuberance for life and this effect on people is astounding. Furthermore, AAI has been researched and its effectiveness on patients’ outcomes and healing is documented. With a soaring trend of the incorporation of complementary therapies into the mainstream of therapy and health care, animal-facilitated therapy has become a popular interest for the therapy team to integrate into a patient’s plan of therapy

Flavor Symmetry and Topology Change in Nuclear Symmetry Energy for Compact Stars

The nuclear symmetry energy figures crucially in the structure of asymmetric nuclei and, more importantly, in the equation of state (EoS) of compact stars. At present it is almost totally unknown, both experimentally and theoretically, in the density regime appropriate for the interior of neutron stars. Basing on a strong-coupled structure of dense baryonic matter encoded in the skyrmion crystal approach with a topology change and resorting to the notion of generalized HLS (hidden local symmetry) in hadronic interactions, we address a variety of hitherto unexplored issues of nuclear interactions associated with the symmetry energy, i.e., kaon condensation and hyperons, possible topology change in dense matter, nuclear tensor forces, conformal symmetry and chiral symmetry etc in the EoS of dense compact-star matter. One of the surprising results coming from the hidden local symmetry structure that is distinct from what is given by standard phenomenological approaches is that at high density, baryonic matter is driven by RG flow to the "dilaton-limit fixed point (DLFP)" constrained by "mended symmetries." We further propose how to formulate kaon condensation and hyperons in compact-star matter in a framework anchored on a single effective Lagrangian by treating hyperons as the Callan-Klebanov kaon-skyrmion bound states simulated on crystal lattice. This formulation suggests that hyperons can figure in the stellar matter -- if at all -- when or after kaons condense, in contrast to the standard phenomenological approaches where the hyperons appear as the first strangeness degree of freedom in matter thereby suppressing or delaying kaon condensation. In our simplified description of the stellar structure in terms of symmetry energies which is compatible with that of the 1.97 solar mass star, kaon condensation plays a role of "doorway state" to strange-quark matter.Comment: 48 pages, 6 figures, version for publicatio

Mesons and nucleons from holographic QCD in a unified approach

We investigate masses and coupling constants of mesons and nucleons within a hard wall model of holographic QCD in a unified approach. We first examine an appropriate form of fermionic solutions by restricting the mass coupling for the five dimensional bulk fermions and bosons. We then derive approximated analytic solutions for the nucleons and the corresponding masses in a small mass coupling region. In order to treat meson and nucleon properties on the same footing, we introduce the same infrared (IR) cut in such a way that the meson-nucleon coupling constants, i.e., g_{pi NN} and g_{rho NN} are uniquely determined. The first order approximation with respect to a dimensionless expansion parameter, which is valid in the small mass coupling region, explicitly shows difficulties to avoid the IR scale problem of the hard wall model. We discuss possible ways of circumventing these problems.Comment: 15 pages, No figure. Several typos have been remove

Bandgap and Band Offsets Determination of Semiconductor Heterostructures using Three-terminal Ballistic Carrier Spectroscopy

Utilizing three-terminal tunnel emission of ballistic electrons and holes, we have developed a method to self-consistently measure the bandgap of semiconductors and band discontinuities at semiconductor heterojunctions without any prerequisite material parameter. Measurements are performed on lattice-matched GaAs/AlxGa1-xAs and GaAs/(AlxGa1-x)0.51In0.49P single-barrier heterostructures. The bandgaps of AlGaAs and AlGaInP are measured with a resolution of several meV at 4.2 K. For the GaAs/AlGaAs interface, the measured Gamma band offset ratio is 60.4:39.6 (+/-2%). For the GaAs/AlGaInP interface, this ratio varies with the Al mole fraction and is distributed more in the valence band. A non-monotonic Al composition dependence of the conduction band offset at the GaAs/AlGaInP interface is observed in the indirect-gap regime.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett