W. H. Wong

Nonspecular effects on reflection from absorbing media at and around Brewster's dip.

We show that, for a TM (or p-state) Gaussian beam incident onto an absorbing medium at and around Brewsters dip, the reflected beam always remains Gaussian and undergoes a Goos-Hänchen-like (GH) shift, an angular shift, a focal shift, and a beam-waist modification, provided that the beam is sufficiently collimated that the third-order change of the (logarithmic) reflection coefficient can be ignored in the angular range of beam divergence. For weak absorption, not only are a large negative GH shift and an odd-functioned-like focal shift with greater magnitude found but also the angular shift, though small by itself, is shown to give an even larger lateral net shift at a distance beyond the Rayleigh range.

Understanding wave characteristics via linear superposition of retarded fields

The Feynman–Schwartz method of linearly superposing retarded fields to understand the origin of the refractive index is generalized to an obliquely incident electromagnetic wave interacting with a planar medium. Different integral equations for the wave field in the medium are obtained for the TE-state and the TM-state of wave polarization. The two states of polarization are shown to satisfy the same differential equation for the spatial variation of the fields and thus they have the same dispersion relation (or the index of refraction) and change of phase velocity upon penetration into the medium. The integral equations are also used to deduce the well-known reflection and transmission coefficients in various cases.

Optimal coupled-cluster approximation for the linear E-e Jahn-Teller effect

Abstract By introducing a slight modification to the successive coupled-cluster approximation, we have developed an optimal coupled-cluster approximation, which can take care of both the accuracies of the ground-state energy and wavefunction estimates, for the ground state of the linear E - e Jahn-Teller effect. Over the whole range of the coupling parameter, our results up to the third level of approximation show good agreement with the exact numerical diagonalization results and are better than those from earlier analytical treatments. The mathematical treatment in this work is simple and could be easily extended to the studies of other fermion-boson interacting systems.

Ground state of a simple spin-boson system: exact results

Abstract The ground state of a two-level system coupled to a dispersionless phonon bath is studied. The exact ground-state solution to the problem is obtained via a combination of unitary transformations and numerical diagonalization. The impossibility of the discontinuous localization-delocalization transition of the tunneling particle is shown.

Ground‐state properties for an easy‐plane spin‐one antiferromagnet— The coupled‐cluster method (abstract)

Using the coupled‐cluster method we investigate the ground‐state properties of an easy‐plane spin‐one antiferromagnet which has a critical point at zero temperature. This spin system represents a nontrivial system with the single‐ion anisotropy. Single‐ion anisotropies have a fundamental influence on the behavior of a magnetic system, and prevail in almost all physical systems with spin greater than one half. Because of the complexities caused by the single‐ion anisotropy term, the mean‐field approximation is commonly used in calculations of the thermodynamic quantities. However, in the mean‐field approximation both quantum and spin fluctuation correlations have been neglected. Here we apply the coupled‐cluster method to obtain the ground‐state energy, staggered magnetization and critical point for both two and three dimensional lattices. In the coupled‐cluster method the correlations of the quantum and spin fluctuations have been systematically included.