Quantum Theory at Surfaces and Interfaces

The electron states around a discontinuity of the otherwise periodic potential of the solid can be found by matching the general solutions in the two regions at the boundary with continuous amplitude and derivative. To set up the general solution, one has to study the complex-k band structure. After introducing the complex-k solutions through a simple example, the general behaviour of the complex bands is investigated. The application of the matching procedure in the calculation of surface states and LEED intensities is discussed. Finally, the tight-binding approach to surface states is outlined. (author)