11,988 research outputs found
Kawasaki-type Dynamics: Diffusion in the kinetic Gaussian model
In this article, we retain the basic idea and at the same time generalize
Kawasaki's dynamics, spin-pair exchange mechanism, to spin-pair redistribution
mechanism, and present a normalized redistribution probability. This serves to
unite various order-parameter-conserved processes in microscopic, place them
under the control of a universal mechanism and provide the basis for further
treatment. As an example of the applications, we treated the kinetic Gaussian
model and obtained exact diffusion equation. We observed critical slowing down
near the critical point and found that, the critical dynamic exponent z=1/nu=2
is independent of space dimensionality and the assumed mechanism, whether
Glauber-type or Kawasaki-type.Comment: accepted for publication in PR
Effect of polar discontinuity on the growth of LaNiO3/LaAlO3 superlattices
We have conducted a detailed microscopic investigation of [LaNiO3(1
u.c.)/LaAlO3(1 u.c.)]N superlattices grown on (001) SrTiO3 and LaAlO3 to
explore the influence of polar mismatch on the resulting electronic and
structural properties. Our data demonstrate that the initial growth on the
non-polar SrTiO3 surface leads to a rough morphology and unusual 2+ valence of
Ni in the first LaNiO3 layer, which is not observed after growth on the polar
surface of LaAlO3. A newly devised model suggests that the polar mismatch can
be resolved if the perovskite layers grow with an excess of LaO, which also
accounts for the observed electronic, chemical, and structural effects.Comment: 3 pages, 3 figure
Weakly nonlinear quantum transport: an exactly solvable model
We have studied the weakly non-linear quantum transport properties of a
two-dimensional quantum wire which can be solved exactly. The non-linear
transport coefficients have been calculated and interesting physical properties
revealed. In particular we found that as the incoming electron energy
approaches a resonant point given by energy , where the transport is
characterized by a complete reflection, the second order non-linear conductance
changes its sign. This has interesting implications to the current-voltage
characteristics. We have also investigated the establishment of the gauge
invariance condition. We found that for systems with a finite scattering
region, correction terms to the theoretical formalism are needed to preserve
the gauge invariance. These corrections were derived analytically for this
model.Comment: 15 pages, LaTeX, submitted to Phys. Rev.
Pairing Symmetry in Iron-Pnictide Superconductor KFeAs
The pairing symmetry is one of the major issues in the study of iron-based
superconductors. We adopt a low-energy effective kinetic model based on the
first-principles band structure calculations combined with the -
model for KFeAs, the phase diagram of pairing symmetries is
constructed. Putting the values of and of the - model
obtained by the first-principles calculations into this phase diagram, we find
that the pairing symmetry for KFeAs is a nodal -wave in the
folded Brillouin zone with two iron atoms per unit cell. This is in good
agreement with experiments observed a nodal order parameter.Comment: 5 pages, 4 figures (The pairing symmetry is dependent on choosing an
effective tight-binding model. In the publication version, we adopt a
ten-orbital model by using the maximally localized Wannier functions based on
the first-principles band structure calculations, and give an s-wave pairing
for KFeAs
New molecular candidates: X(1910), X(2200), and X(2350)
Assuming the newly observed resonant structures X(1910), X(2200), and X(2350)
as , , and molecular states respectively,
we compute their mass values in the framework of QCD sum rules. The numerical
results are for state,
for state, and for state, which
coincide with the experimental values of X(1910), X(2200), and X(2350),
respectively. This supports the statement that X(1910), X(2200), and X(2350)
could be , , and molecular candidates
respectively.Comment: 9 pages, 9 eps figures; the name of X(2000) changed to X(1910)
according to the updated data of experiments; more references and discussions
added; accepted for publication in PRD. arXiv admin note: substantial text
overlap with arXiv:1211.2277, arXiv:1201.341
Entanglement-assisted local operations and classical communications conversion in the quantum critical systems
Conversions between the ground states in quantum critical systems via
entanglement-assisted local operations and classical communications (eLOCC) are
studied. We propose a new method to reveal the different convertibility by
local operations when a quantum phase transition occurs. We have studied the
ground state local convertibility in the one dimensional transverse field Ising
model, XY model and XXZ model. It is found that the eLOCC convertibility sudden
changes at the phase transition points. In transverse field Ising model the
eLOCC convertibility between the first excited state and the ground state are
also distinct for different phases. The relation between the order of quantum
phase transitions and the local convertibility is discussed.Comment: 7 pages, 5 figures, 5 table
Dynamic critical exponents of Swendsen-Wang and Wolff algorithms by nonequilibrium relaxation
With a nonequilibrium relaxation method, we calculate the dynamic critical
exponent z of the two-dimensional Ising model for the Swendsen-Wang and Wolff
algorithms. We examine dynamic relaxation processes following a quench from a
disordered or an ordered initial state to the critical temperature T_c, and
measure the exponential relaxation time of the system energy. For the
Swendsen-Wang algorithm with an ordered or a disordered initial state, and for
the Wolff algorithm with an ordered initial state, the exponential relaxation
time fits well to a logarithmic size dependence up to a lattice size L=8192.
For the Wolff algorithm with a disordered initial state, we obtain an effective
dynamic exponent z_exp=1.19(2) up to L=2048. For comparison, we also compute
the effective dynamic exponents through the integrated correlation times. In
addition, an exact result of the Swendsen-Wang dynamic spectrum of a
one-dimension Ising chain is derived.Comment: 13 pages, 6 figure
- …