2004/08/31 by M. Lüders, M. A. L. Marques, N. N. Lathiotakis +6 · 1 citation
Physics and Astronomy · #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.72.024545
published as Phys.Rev.B72:024545,2005 · 18 pages, 4 figures, 1 table, revised version
arxiv created 2005/08/31 · arxiv updated 2009/12/01
A novel approach to the description of superconductors in thermal equilibrium is developed within a formally exact density-functional framework. The theory is formulated in terms of three ``densities'': the ordinary electron density, the superconducting order parameter, and the diagonal of the nuclear N-body density matrix. The electron density and the order parameter are determined by Kohn-Sham equations that resemble the Bogoliubov-de Gennes equations. The nuclear density matrix follows from a Schroedinger equation with an effective N-body interaction. These equations are coupled to each other via exchange-correlation potentials which are universal functionals of the three densities. Approximations of these exchange-correlation functionals are derived using the diagrammatic techniques of many-body perturbation theory. The bare Coulomb repulsion between the electrons and the electron-phonon interaction enter this perturbative treatment on the same footing. In this way, a truly ab-initio description is achieved which does not contain any empirical parameters.