20,159 research outputs found
Detection of spin voltaic effect in a p-n heterojunction
Model calculation and experimental data of
circularly-polarized-light-dependent photocurrent in a n-AlGaAs/p-InGaAs/p-GaAs
heterostructure are reported. It is found that, under the appropriate forward
bias condition, spin voltaic effect (SVE) can survive across the heterojunction
and give rise to detectable polarization-dependent photocurrent signals which
are greater than the signals due to the magnetic circular dichroism. Our
analysis suggests that SVE can be enhanced by optimization of layer thickness,
doping profile, and applied bias, making SVE favorable for the realization of a
semiconductor-based polarization detector, a spin-photodiode (spin-PD).Comment: 16 pages, 3figure
ppK- bound states from Skyrmions
The bound kaon approach to the strangeness in the Skyrme model is applied to
investigating the possibility of deeply bound states. We describe the
system as two-Skyrmion around which a kaon field fluctuates. Each
Skyrmion is rotated in the space of SU(2) collective coordinate. The rotational
motions are quantized to be projected onto the spin-singlet proton-proton
state. We derive the equation of motion for the kaon in the background field of
two Skyrmions at fixed positions. From the numerical solution of the equation
of motion, it is found that the energy of can be considerably small, and
that the distribution of shows molecular nature of the system.
For this deep binding, the Wess-Zumino-Witten term plays an important role. The
total energy of the system is estimated in the Born-Oppenheimer
approximation. The binding energy of the state is MeV.
The mean square radius of the subsystem is
fm.Comment: Oct 2007, 15 pages, 8 figures; added references, corrected typo
Single crystal growth and physical properties of SrFe(AsP)
We report a crystal growth and physical properties of
SrFe(AsP). The single crystals for various s were
grown by a self flux method. For , reaches the maximum value of
30\,K and the electrical resistivity () shows -linear dependence.
As increases, decreases and () changes to -behavior,
indicating a standard Fermi liquid. These results suggest that a magnetic
quantum critical point exists around .Comment: 4 pages, 4 figures, accepted to Supplemental issue of the Journal of
Physical Society of Japan (JPSJ
Model-independent study of the QCD sum rule for the pi NN coupling constant
We reinvestigate the QCD sum rule for the pi NN coupling constant, g,
starting from the vacuum-to-pion matrix element of the correlation function of
the interpolating fields of two nucleons. We study in detail the physical
content of the correlation function without referring to the effective theory.
We consider the invariant correlation functions by splitting the correlation
function into different Dirac structures. We show that the coefficients of the
double-pole terms are proportional to g but that the coefficients of the
single-pole terms are not determined by g. In the chiral limit the single-pole
terms as well as the continuum terms are ill defined in the dispersion
integral. Therefore, the use of naive QCD sum rules obtained from the invariant
correlation functions is not justified. A possible procedure to avoid this
difficulty is discussed.Comment: 20 pages, 2 figure
On Measuring the top quark mass using the dilepton decay modes
We demonstrate a new likelihood method for extracting the top quark mass from
events of the type ttbar-->bW(l+nu)bW(l+nu) This method estimates the top quark
mass correctly from an ensemble of dilepton events. The method proposed by
Dalitz and Goldstein [1] is shown to result in a systematic underestimation of
the top quark mass. Effects due to the spin correlations between the top and
anti-top quarks are shown to be unimportant in estimating the mass of the top
quark.Comment: To appear in the proceedings of the 1996 DPF/DPB study on new
directions for High Energy Physics, Snowmass, Colorad
Dynamical mass generation in quantum field theory : some methods with application to the Gross-Neveu model and Yang-Mills theory
We introduce some techniques to investigate dynamical mass generation. The
Gross-Neveu model (GN) is used as a toy model, because the GN mass gap is
exactly known, making it possible to check reliability of the various methods.
Very accurate results are obtained. Also application to SU(N) Yang-Mills (YM)
is discussed.Comment: 8 LaTeX2e pages, uses Kluwer class file crckbked.cls. Kluwer package
included. To appear in: Proceedings of the NATO Advanced Research Workshop on
"Confinement, Topology, and other Non-Perturbative Aspects of QCD", Stara
Lesna, Slovakia, 21-27 jan 200
Realization of Strong Coupling Fixed Point in Multilevel Kondo Models
Impurity four- and six-level Kondo model, in which an ion is tunneling among
four- and six-stable points and interacting with surrounding conduction
electrons, are investigated by using the perturbative and numerical
renormalization group methods. It is shown that purely orbital Kondo effects
occur at low temperatures in these systems which are direct generalizations of
the Kondo effect in the so-called two-level system. This result offers a good
explanation for the enhanced and magnetically robust Sommerfeld coefficient
observed in SmOs_4Sb_12 and some other filled-skutterudites.Comment: 3 pages, 3 figures, for proceedings of ASR-WYP-2005. To be published
in Journal of Physical Society Japan supplemen
Two-band Fluctuation Exchange Study on the Superconductivity of -(BEDT-TTF)ICl under High Pressure
We study the pressure dependence of the superconducting transition
temperature of an organic superconductor -(BEDT-TTF)ICl by
applying the fluctuation exchange method to the Hubbard model on the original
two-band lattice at 3/4-filling rather than the single band model in the strong
dimerization limit. Our study is motivated by the fact that hopping parameters
evaluated from a first-principles study suggest that the dimerization of the
BEDT-TTF molecules is not so strong especially at high pressure. Solving the
linearized Eliashberg's equation, a d-wave-like superconducting state
with realistic values of is obtained in a pressure regime somewhat higher
than the actual experimental result. These results are similar to those
obtained within the single band model in the previous study by Kino {\it et
al}. We conclude that the resemblance to the dimer limit is due to a
combination of a good Fermi surface nesting, a large density of states near the
Fermi level, and a moderate dimerization, which cooperatively enhance electron
correlation effects and also the superconducting .Comment: 6 pages, 8 figure
Superconductivity in Organic Compounds with Pseudo-Triangular Lattice
We study spin fluctuation (SF) mediated superconductivity (SC) in a
half-filled square lattice Hubbard model with the transfer matrices -t between
nearest neighbor sites and -t' between a half of next nearest neighbor sites
neighboring along only one of the directions, considering application of
this model to organic kappa-(BEDT-TTF)2X compounds. Varying the t'/t value from
0 to 1, one can interpolate between a square and an equilateral triangular
lattice, the latter giving frustration to antiferromagnetically (AF) coupled
spin systems. Within the fluctuation exchange (FLEX) approximation, we
calculate chi(q,omega), Tc and the SC order parameter for various model
parameter values and find that both AF and SC are suppressed as one approaches
the frustration geometry or |(t'/t)-1| \to 0. The SC phase, however, extends
beyond the AF phase boundary fairly close to t'/t=1 for realistic U/t values.
The order parameter is of x2-y2-type for t'/t1.Comment: 4 pages, 5 eps figures, to appear in J. Phys. Soc. Jp
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