General boundary conditions for the envelope function in multiband k.p model

We have derived general boundary conditions (BC) for the multiband envelope functions (which do not contain spurious solutions) in semiconductor heterostructures with abrupt heterointerfaces. These BC require the conservation of the probability flux density normal to the interface and guarantee that the multiband Hamiltonian be self--adjoint. The BC are energy independent and are characteristic properties of the interface. Calculations have been performed of the effect of the general BC on the electron energy levels in a potential well with infinite potential barriers using a coupled two band model. The connection with other approaches to determining BC for the envelope function and to the spurious solution problem in the multiband k.p model are discussed.Comment: 15 pages, 2 figures; to be published in Phys. Rev. B 65, March 15 issue 200

On a unique continuum representation for the linear chain problem

An exact unique continuum representation for the one-dimensional linear chain problem has been constructed. Some aspects of intermediate approximations are discussed

On a class of scattering equations

In this paper a class of conservative wave equations treated by Broer and Peletier is considered when a single localised scatterer is present. A criterion for stability in the energy norm is derived. The formal solution of the scattering problem is given. The relation between the location of poles of the scattering matrix, the occurrence of standing wave solutions and the energy criterion is discussed

On a simple wave approximation

An approximation (the linear version of Burgers' equation with appropriate initial data) to a simple wave initial value problem for a set of two linear coupled dissipative partial differential equations is discussed. It has been shown that for the class of square integrable initial functions of which the spectra (Fourier-transforms) have bounded support 2 the approximation is valid for some finite interval of time [0, T()]. For some finite timeT 1 > T() the approximation may fail. However, fort, it is asymptotically valid again. For the class of initial conditions mentioned above expansions in series of the two solutions, which for every finite interval of time [0, ] are convergent, may be constructed