63,318 research outputs found
Systematic {\it ab initio} study of the magnetic and electronic properties of all 3d transition metal linear and zigzag nanowires
It is found that all the zigzag chains except the nonmagnetic (NM) Ni and
antiferromagnetic (AF) Fe chains which form a twisted two-legger ladder, look
like a corner-sharing triangle ribbon, and have a lower total energy than the
corresponding linear chains. All the 3d transition metals in both linear and
zigzag structures have a stable or metastable ferromagnetic (FM) state. The
electronic spin-polarization at the Fermi level in the FM Sc, V, Mn, Fe, Co and
Ni linear chains is close to 90% or above. In the zigzag structure, the AF
state is more stable than the FM state only in the Cr chain. It is found that
the shape anisotropy energy may be comparable to the electronic one and always
prefers the axial magnetization in both the linear and zigzag structures. In
the zigzag chains, there is also a pronounced shape anisotropy in the plane
perpendicular to the chain axis. Remarkably, the axial magnetic anisotropy in
the FM Ni linear chain is gigantic, being ~12 meV/atom. Interestingly, there is
a spin-reorientation transition in the FM Fe and Co linear chains when the
chains are compressed or elongated. Large orbital magnetic moment is found in
the FM Fe, Co and Ni linear chains
Triaxiality and shape coexistence in Germanium isotopes
The ground-state deformations of the Ge isotopes are investigated in the
framework of Gogny-Hartree-Fock-Bogoliubov (HFB) and Skyrme Hartree-Fock plus
pairing in the BCS approximation. Five different Skyrme parametrizations are
used to explore the influence of different effective masses and spin-orbit
models. There is generally good agreement for binding energies and deformations
(total quadrupole moment, triaxiality) with experimental data where available
(i.e., in the valley of stability). All calculations agree in predicting a
strong tendency for triaxial shapes in the Ge isotopes with only a few
exceptions due to neutron (sub-)shell closures. The frequent occurrence of
energetically very close shape isomers indicates that the underlying
deformation energy landscape is very soft. The general triaxial softness of the
Ge isotopes is demonstrated in the fully triaxial potential energy surface. The
differences between the forces play an increasing role with increasing neutron
number. This concerns particularly the influence of the spin-orbit model, which
has a visible effect on the trend of binding energies towards the drip line.
Different effective mass plays an important role in predicting the quadrupole
and triaxial deformations. The pairing strength only weakly affects binding
energies and total quadrupole deformations, but considerably influences
triaxiality.Comment: 9 page
Observation of an in-plane magnetic-field-driven phase transition in a quantum Hall system with SU(4) symmetry
In condensed matter physics, the study of electronic states with SU(N)
symmetry has attracted considerable and growing attention in recent years, as
systems with such a symmetry can often have a spontaneous symmetry-breaking
effect giving rise to a novel ground state. For example, pseudospin quantum
Hall ferromagnet of broken SU(2) symmetry has been realized by bringing two
Landau levels close to degeneracy in a bilayer quantum Hall system. In the past
several years, the exploration of collective states in other multi-component
quantum Hall systems has emerged. Here we show the conventional pseudospin
quantum Hall ferromagnetic states with broken SU(2) symmetry collapsed rapidly
into an unexpected state with broken SU(4) symmetry, by in-plane magnetic field
in a two-subband GaAs/AlGaAs two-dimensional electron system at filling factor
around . Within a narrow tilting range angle of 0.5 degrees, the
activation energy increases as much as 12 K. While the origin of this puzzling
observation remains to be exploited, we discuss the possibility of a
long-sought pairing state of electrons with a four-fold degeneracy.Comment: 13 pages, 4 figure
A non-variational approach to nonlinear stability in stellar dynamics applied to the King model
In previous work by Y. Guo and G. Rein, nonlinear stability of equilibria in
stellar dynamics, i.e., of steady states of the Vlasov-Poisson system, was
accessed by variational techniques. Here we propose a different,
non-variational technique and use it to prove nonlinear stability of the King
model against a class of spherically symmetric, dynamically accessible
perturbations. This model is very important in astrophysics and was out of
reach of the previous techniques
Plasmon assisted transmission of high dimensional orbital angular momentum entangled state
We present an experimental evidence that high dimensional orbital angular
momentum entanglement of a pair of photons can be survived after a
photon-plasmon-photon conversion. The information of spatial modes can be
coherently transmitted by surface plasmons. This experiment primarily studies
the high dimensional entangled systems based on surface plasmon with
subwavelength structures. It maybe useful in the investigation of spatial mode
properties of surface plasmon assisted transmission through subwavelength hole
arrays.Comment: 7 pages,6 figure
Effective generation of Ising interaction and cluster states in coupled microcavities
We propose a scheme for realizing the Ising spin-spin interaction and atomic
cluster states utilizing trapped atoms in coupled microcavities. It is shown
that the atoms can interact with each other via the exchange of virtual photons
of the cavities. Through suitably tuning the parameters, an effective Ising
spin-spin interaction can be generated in this optical system, which is used to
produce the cluster states. This scheme does not need the preparation of
initial states of atoms and cavity modes, and is insensitive to cavity decay.Comment: 11pages, 2 figures, Revtex
Perturbative analysis of generally nonlocal spatial optical solitons
In analogy to a perturbed harmonic oscillator, we calculate the fundamental
and some other higher order soliton solutions of the nonlocal nonlinear
Schroedinger equation (NNLSE) in the second approximation in the generally
nonlocal case. Comparing with numerical simulations we show that soliton
solutions in the 2nd approximation can describe the generally nonlocal soliton
states of the NNLSE more exactly than that in the zeroth approximation. We show
that for the nonlocal case of an exponential-decay type nonlocal response the
Gaussian-function-like soliton solutions can't describe the nonlocal soliton
states exactly even in the strongly nonlocal case. The properties of such
nonlocal solitons are investigated. In the strongly nonlocal limit, the
soliton's power and phase constant are both in inverse proportion to the 4th
power of its beam width for the nonlocal case of a Gaussian function type
nonlocal response, and are both in inverse proportion to the 3th power of its
beam width for the nonlocal case of an exponential-decay type nonlocal
response.Comment: 13 pages, 16 figures, accepted by Phys. Rev.
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