Equilibrium and dynamical properties of the ANNNI chain at the multiphase point

We study the equilibrium and dynamical properties of the ANNNI (axial next-nearest-neighbor Ising) chain at the multiphase point. An interesting property of the system is the macroscopic degeneracy of the ground state leading to finite zero-temperature entropy. In our equilibrium study we consider the effect of softening the spins. We show that the degeneracy of the ground state is lifted and there is a qualitative change in the low temperature behaviour of the system with a well defined low temperature peak of the specific heat that carries the thermodynamic ``weight'' of the ground state entropy. In our study of the dynamical properties, the stochastic Kawasaki dynamics is considered. The Fokker-Planck operator for the process corresponds to a quantum spin Hamiltonian similar to the Heisenberg ferromagnet but with constraints on allowed states. This leads to a number of differences in its properties which are obtained through exact numerical diagonalization, simulations and by obtaining various analytic bounds.Comment: 9 pages, RevTex, 6 figures (To appear in Phys. Rev. E

Guiding and confining fast electrons by transient electric and magnetic fields with a plasma inverse cone

Copyright 2009 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 16(2), 020702, 2009 and may be found at http://dx.doi.org/10.1063/1.307592

The controlled teleportation of an arbitrary two-atom entangled state in driven cavity QED

In this paper, we propose a scheme for the controlled teleportation of an arbitrary two-atom entangled state $|\phi>_{12}=a|gg>_{12}+b|ge>_{12}+c|eg>_{12}+d|ee>_{12}$ in driven cavity QED. An arbitrary two-atom entangled state can be teleported perfectly with the help of the cooperation of the third side by constructing a three-atom GHZ entangled state as the controlled channel. This scheme does not involve apparent (or direct) Bell-state measurement and is insensitive to the cavity decay and the thermal field. The probability of the success in our scheme is 1.0.Comment: 10 page

Spin-polarized ballistic transport in a thin superlattice of zinc blende half-metallic compounds

We examine theoretically ballistic conduction in thin layers of zinc blende half metals, considering as an example a superlattice consisting of monolayers of GaAs and MnAs, a bilayer of CrAs, and a bilayer of GaAs. By artificially separating bilayers, we show that surface states thwart half metallicity. However, capping the metal-As bilayers restores half metallicity, and ballistic conduction of electrons within ∼0.3 eV of the Fermi level will give nearly 100% spin-polarized transmission in the direction of the superlattice. Recent developments suggest atomic layer epitaxy can be used to produce such thin layers for spintronic applications. ©2005 The American Physical Society

Experimental Study on Seismic Behavior of Cluster-Reinforced Precast Concrete Columns with Grouting-Anchor Connections

The prefabricated residential buildings have become one of the most dominating construction methods in the modern construction industry. The seismic behavior of prefabricated components is crucial in the limit state design of the precast structure. This paper investigates the seismic behavior of a new type precast concrete column that has clustered steel reinforcement with grouting connection. Quasi-static tests are carried out on three cast-in-situ columns and seven precast columns. Axial compression ratio, lap length and lap space are the main variables considered. The failure process, hysteresis curve, skeleton curve, stiffness degradation, displacement ductility and energy dissipation are elaborated. The experimental results show that the precast columns with cluster reinforcement have similar seismic behavior to the cast-in-situ columns. Reducing the axial pressure can improve the ductility and energy consumption performance of the cluster-reinforced columns and exert its ductility to improve its seismic performance. During the assembly, a moderate increase in lap length can improve the seismic behavior of precast columns, whereas the lap space has an insignificant effect on the seismic behavior which indicates that the lap space is not an important factor during construction. The research outcome can serve as a reference for further development and application of precast structures