1,980 research outputs found
Identification of the major physiologic phosphorylation site of human keratin 18: potential kinases and a role in filament reorganization.
Exchange Biasing of the Ferromagnetic Semiconductor Ga1-xMnxAs
We demonstrate the exchange coupling of a ferromagnetic semiconductor
(Ga1-xMnxAs) with an overgrown antiferromagnet (MnO). Unlike most conventional
exchange biased systems, the blocking temperature of the antiferromagnet (T_B =
48 +- 2 K) and the Curie temperature of the ferromagnet (T_C = 55.1 +- 0.2 K)
are comparable. The resulting exchange bias manifests itself as a clear shift
in the magnetization hysteresis loop when the bilayer is cooled in the presence
of an applied magnetic field and an enhancement of the coercive field.Comment: pdf file only; submitted to Applied Physics Letter
Exchange Biasing of the Ferromagnetic Semiconductor (Ga,Mn)As by MnO
We provide an overview of progress on the exchange biasing of a ferromagnetic
semiconductor (Ga1-xMnxAs) by proximity to an antiferromagnetic oxide layer
(MnO). We present a detailed characterization study of the antiferromagnetic
layer using Rutherford backscattering spectrometry, x-ray photoelectron
spectroscopy, transmission electron microscopy, and x-ray reflection. In
addition, we describe the variation of the exchange and coercive fields with
temperature and cooling field for multiple samples.Comment: To appear in J. Appl. Phys. (invited paper in Proceedings of the 49th
Annual Conference on Magnetism & Magnetic Materials); pdf file onl
Feynman diagrams versus Fermi-gas Feynman emulator
Precise understanding of strongly interacting fermions, from electrons in
modern materials to nuclear matter, presents a major goal in modern physics.
However, the theoretical description of interacting Fermi systems is usually
plagued by the intricate quantum statistics at play. Here we present a
cross-validation between a new theoretical approach, Bold Diagrammatic Monte
Carlo (BDMC), and precision experiments on ultra-cold atoms. Specifically, we
compute and measure with unprecedented accuracy the normal-state equation of
state of the unitary gas, a prototypical example of a strongly correlated
fermionic system. Excellent agreement demonstrates that a series of Feynman
diagrams can be controllably resummed in a non-perturbative regime using BDMC.
This opens the door to the solution of some of the most challenging problems
across many areas of physics
Exact Wavefunctions in a Noncommutative Field Theory
We consider the nonrelativistic field theory with a quartic interaction on a
noncommutative plane. We compute the four point scattering amplitude within
perturbative analysis to all orders and identify the beta function and the
running of the coupling constant. Since the theory admits an equivalent
description via the N particle Schrodinger equation, we regain the scattering
amplitude by finding an exact scattering wavefunction of the two body equation.
The wave function for the bound state is also identified. These wave functions
unusually have two center positions in the relative coordinates. The separation
of the centers is in the transverse direction of the total momentum and grows
linearly with the noncommutativity scale and the total momentum, exhibiting the
stringy nature of the noncommutative field theory.Comment: Typos corrected. 7 page
Self-consistent solution of Kohn-Sham equations for infinitely extended systems with inhomogeneous electron gas
The density functional approach in the Kohn-Sham approximation is widely used
to study properties of many-electron systems. Due to the nonlinearity of the
Kohn-Sham equations, the general self-consistence searching method involves
iterations with alternate solving of the Poisson and Schr\"{o}dinger equations.
One of problems of such an approach is that the charge distribution renewed by
means of the Schr\"{o}dinger equation solution does not conform to boundary
conditions of Poisson equation for Coulomb potential. The resulting instability
or even divergence of iterations manifests itself most appreciably in the case
of infinitely extended systems. The published attempts to deal with this
problem are reduced in fact to abandoning the original iterative method and
replacing it with some approximate calculation scheme, which is usually
semi-empirical and does not permit to evaluate the extent of deviation from the
exact solution. In this work, we realize the iterative scheme of solving the
Kohn-Sham equations for extended systems with inhomogeneous electron gas, which
is based on eliminating the long-range character of Coulomb interaction as the
cause of tight coupling between charge distribution and boundary conditions.
The suggested algorithm is employed to calculate energy spectrum,
self-consistent potential, and electrostatic capacitance of the semi-infinite
degenerate electron gas bounded by infinitely high barrier, as well as the work
function and surface energy of simple metals in the jellium model. The
difference between self-consistent Hartree solutions and those taking into
account the exchange-correlation interaction is analyzed. The case study of the
metal-semiconductor tunnel contact shows this method being applied to an
infinitely extended system where the steady-state current can flow.Comment: 38 pages, 9 figures, to be published in ZhETF (J. Exp. Theor. Phys.
Numerical study of the Jahn-Teller polaron and bipolaron
The properties of the polaron and bipolaron are explored in the 1D
Jahn-Teller model with dynamical quantum phonons. The ground-state properties
of the polaron and bipolaron are computed using a recently developed
variational method. Dynamical properties of the ground state of a polaron are
investigated by calculating the optical conductivity . Our
numerical results suggest that the Jahn-Teller and Holstein polarons are
similar. However, in the strong-coupling regime qualitative differences in
between the two models are found and discussed. The influence
of the electron-phonon coupling and the electrostatic repulsion on the
bipolaron binding energy, bipolaron masses, and correlation functions is
investigated.Comment: 9 pages including 11 figures. To appear in PR
Dynamics of human keratin 18 phosphorylation: polarized distribution of phosphorylated keratins in simple epithelial tissues.
The regularized visible fold revisited
The planar visible fold is a simple singularity in piecewise smooth systems.
In this paper, we consider singularly perturbed systems that limit to this
piecewise smooth bifurcation as the singular perturbation parameter
. Alternatively, these singularly perturbed systems can
be thought of as regularizations of their piecewise counterparts. The main
contribution of the paper is to demonstrate the use of consecutive blowup
transformations in this setting, allowing us to obtain detailed information
about a transition map near the fold under very general assumptions. We apply
this information to prove, for the first time, the existence of a locally
unique saddle-node bifurcation in the case where a limit cycle, in the singular
limit , grazes the discontinuity set. We apply this
result to a mass-spring system on a moving belt described by a Stribeck-type
friction law
Noncommutative Field Theories and Smooth Commutative Limits
We consider two model field theories on a noncommutative plane that have
smooth commutative limits. One is the single-component fermion theory with
quartic interaction that vanishes identically in the commutative limit. The
other is a scalar-fermion theory, which extends the scalar field theory with
quartic interaction by adding a fermion. We compute the bound state energies
and the two particle scattering amplitudes exactly.Comment: 8 pages, 2 figure
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