Abstract
We develop the multiband BCS model of superconductivity in the ultrathin films using the orthogonal tight-binding approximation for constructing the electron wave functions. This allows for relatively simple determination of the band structure near the Fermi level as well as the electron-electron interaction matrix elements of the BCS type. The model is applied to the ultrathin films, for which the critical temperature values are calculated in the thickness range layers. The importance of the boundary conditions is emphasized, as either boron or magnesium layers may cover the film. It is found that films thinner than four layers show a substantial decrease in the critical temperature. The charge spillage outside the geometric boundaries of the film, which is allowed in our model, supresses oscillations and weakens its dependence on film covering layer composition.
- Received 4 March 2006
DOI:https://doi.org/10.1103/PhysRevB.74.094501
©2006 American Physical Society