3,866 research outputs found
Effect of Resonant Continuum on Pairing Correlations in the Relativistic Approach
A proper treatment of the resonant continuum is to take account of not only
the energy of the resonant state, but also its width. The effect of the
resonant states on pairing correlations is presented based on the relativistic
mean field theory plus Bardeen-Cooper-Schrieffer(BCS) approximation with a
constant pairing strength. The study is performed in an effective Lagrangian
with the parameter set NL3 for neutron rich even-even Ni isotopes. The results
show that the contribution of the proper treatment of the resonant continuum to
pairing correlations for those nuclei close to neutron drip line is important.
The pairing gaps, Fermi energies, pairing correlation energies, and binding
energies are considerably affected with a proper consideration of the width of
resonant states. The problem of an unphysical particle gas, which may appear in
the calculation of the traditional mean field plus BCS method for nuclei in the
vicinity of drip line could be well overcome when the pairing correlation is
performed by using the resonant states instead of the discretized states in the
continuum.Comment: 19 pages, 8 Postscript figur
A Improved Particle Swarm Optimization Algorithm with Dynamic Acceleration Coefficients
Particle swarm optimization (PSO) is one of the famous heuristic methods. However, this method may suffer to trap at local minima especially for multimodal problem. This paper proposes a modified particle swarm optimization with dynamic acceleration coefficients (ACPSO). To efficiently control the local search and convergence to the global optimum solution, dynamic acceleration coefficients are introduced to PSO. To improve the solution quality and robustness of PSO algorithm, a new best mutation method is proposed to enhance the diversity of particle swarm and avoid premature convergence. The effectiveness of ACPSO algorithm is tested on different benchmarks. Simulation results found that the proposed ACPSO algorithm has good solution quality and more robust than other methods reported in previous work
Electronic band gaps and transport in aperiodic graphene superlattices of Thue-Morse sequence
We have studied the electronic properties in aperiodic graphene superlattices
of Thue-Morse sequence. Although the structure is aperiodic, an unusual Dirac
point (DP) does exist and its location is exactly at the position of the
zero-averaged wave number (zero-. Furthermore, the zero- gap
associated with the DP is robust against the lattice constants and the incident
angles, and multi-DPs can appear under the suitable conditions. A resultant
controllability of electron transport in Thue-Morse sequence is predicted,
which may facilitate the development of many graphene-based electronics.Comment: Accepted for publication in Applied Physics Letters; 4 pagese, 5
figure
Electronic band gaps and transport properties in periodically alternating mono- and bi-layer graphene superlattices
We investigate the electronic band structure and transport properties of
periodically alternating mono- and bi-layer graphene superlattices (MBLG SLs).
In such MBLG SLs, there exists a zero-averaged wave vector
(zero-) gap that is insensitive to the lattice constant. This
zero- gap can be controlled by changing both the ratio of the
potential widths and the interlayer coupling coefficient of the bilayer
graphene. We also show that there exist extra Dirac points; the conditions for
these extra Dirac points are presented analytically. Lastly, we demonstrate
that the electronic transport properties and the energy gap of the first two
bands in MBLG SLs are tunable through adjustment of the interlayer coupling and
the width ratio of the periodic mono- and bi-layer graphene.Comment: More discussion is added and the English is polished. Accepted for
publication in EP
- …