THE SUPERCONDUCTING PENETRATION DEPTH FROM THE SEMICLASSICAL MODEL

The semiclassical approach of Onsager and Pippard has been very succes sful in relating the electronic properties of a normal metal to its ba nd structure and fermi surface. This paper extends the method to a sup erconductor. A generalized London equation relating the supercurrent d ensity to the vector potential is obtained, in terms of band and fermi surface parameters and an energy gap which may be anisotropic. The re sults allow an interpretation of measured penetration depths directly in terms of the electronic and gap structures of the superconductor. T hey lead to easy physical visualization of the origin of anisotropies and other features of measured penetration depths.