THEORY OF SEMIBALLISTIC WAVE-PROPAGATION

Wave propagation through waveguides, quantum wires, or films with a mo dest amount of disorder is in the semiballistic regime when in the tra nsversal direction(s) almost no scattering occurs, while in the long d irection(s) there is so much scattering that the transport is diffusiv e. For such systems, randomness is modeled by an inhomogeneous density of pointlike scatterers. These are first considered in the second ord er Born approximation and then beyond that approximation. In the latte r case, it is found that attractive point scatterers in a cavity alway s have geometric resonances, even for Schrodinger wave scattering. In the long sample limit, the transport equation is solved analytically. Various geometries are considered: waveguides, films, and tunneling ge ometries such as Fabry-Perot interferometers and double-barrier quantu m wells. The predictions are compared with new and existing numerical data and with experiment. The agreement is quite satisfactory.