Theory of relativistic effects in superconductors

We develop a relativistic generalization of the Bogoliubov-de Gennes equati ons where the particle and hole amplitudes are Dirac spinors. In the weakly relativistic limit, we find, besides the usual spin-orbit, Darwin and kine tic energy corrections, additional 'spin-orbit' and 'Darwin' terms. These n ew terms are present in superconductors only and involve the pairing field in place of the electrostatic potential. They become relevant for supercond uctors such as the heavy-fermions and high-T-c compounds, which are charact erized by a short coherence length and heavy elements in the lattice. (C) 1 999 Elsevier Science B.V. All rights reserved.