37,675 research outputs found
Algebraic approach to the Hulthen potential
In this paper the energy eigenvalues and the corresponding eigenfunctions are
calculated for Hulthen potential. Then we obtain the ladder operators and show
that these operators satisfy SU(2) commutation relation.Comment: 8 Pages, 1 Tabl
Mesoscopic Kondo effect of a quantum dot embedded in an Aharonov-Bohm ring with intradot spin-flip scattering
We study the Kondo effect in a quantum dot embedded in a mesoscopic ring
taking into account intradot spin-flip scattering . Based on the finite-
slave-boson mean-field approach, we find that the Kondo peak in the density of
states is split into two peaks by this coherent spin-flip transition, which is
responsible for some interesting features of the Kondo-assisted persistent
current circulating the ring: (1) strong suppression and crossover to a sine
function form with increasing ; (2) appearance of a "hump" in the
-dependent behavior for odd parity. -induced reverse of the persistent
current direction is also observed for odd parity.Comment: 7 pages,6 figures, to be published by Europhys. Let
The Volume Source Technique for flavor singlets: a second look
We reconsider the Volume Source Technique (VST) for the determination of
flavor singlet quantities on the lattice. We point out a difficulty arising in
the case of fermions in real representations of the gauge group and propose an
improved version of the method (IVST) based on random gauge transformations of
the background configuration. We compare the performance of IVST with the
method based on stochastic estimators (SET). We consider the case of the N=1
Supersymmetric Yang-Mills Theory (SYM), where just one fermionic flavor is
present, the gluino in the adjoint representation, and only flavor singlet
states are possible. The work is part of an inclusive analysis of the spectrum
of the lightest particles of the theory, based on the simulation of the model
on a lattice with dynamical gluinos in the Wilson scheme.Comment: 11 pages, 6 figures, some formulations change
Two successive field-induced spin-flop transitions in single-crystalline CaCoAs
CaCoAs, a ThCrSi-structure compound, undergoes an
antiferromagnetic transition at \emph{T}=76K with the magnetic moments
being aligned parallel to the \emph{c} axis. Electronic transport measurement
reveals that the coupling between conducting carriers and magnetic order in
CaCoAs is much weaker comparing to the parent compounds of iron
pnictide. Applying magnetic field along \emph{c} axis induces two successive
spin-flop transitions in its magnetic state. The magnetization saturation
behaviors with \emph{\textbf{H}c} and \emph{\textbf{H}ab}
at 10K indicate that the antiferromagnetic coupling along \emph{c} direction is
very weak. The interlayer antiferromagntic coupling constant \emph{J} is
estimated to be about 2 meV.Comment: Accepted for publication in Phys. Rev. B. 5 pages, 6 figure
A Noisy Monte Carlo Algorithm
We propose a Monte Carlo algorithm to promote Kennedy and Kuti's linear
accept/reject algorithm which accommodates unbiased stochastic estimates of the
probability to an exact one. This is achieved by adopting the Metropolis
accept/reject steps for both the dynamical and noise configurations. We test it
on the five state model and obtain desirable results even for the case with
large noise. We also discuss its application to lattice QCD with stochastically
estimated fermion determinants.Comment: 10 pages, 1 tabl
Superconductivity at 41 K and its competition with spin-density-wave instability in layered CeOFFeAs
A series of layered CeOFFeAs compounds with x=0 to 0.20 are
synthesized by solid state reaction method. Similar to the LaOFeAs, the pure
CeOFeAs shows a strong resistivity anomaly near 145 K, which was ascribed to
the spin-density-wave instability. F-doping suppresses this instability and
leads to the superconducting ground state. Most surprisingly, the
superconducting transition temperature could reach as high as 41 K. The very
high superconducting transition temperature strongly challenges the classic BCS
theory based on the electron-phonon interaction. The very closeness of the
superconducting phase to the spin-density-wave instability suggests that the
magnetic fluctuations play a key role in the superconducting paring mechanism.
The study also reveals that the Ce 4f electrons form local moments and ordered
antiferromagnetically below 4 K, which could coexist with superconductivity.Comment: 4 pages, 5 figure
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