JOURNAL OF PHYSICS-CONDENSED MATTER, cilt.6, sa.11, ss.2245-2258, 1994 (SCI-Expanded)
By using the Gor'kov-Nambu microscopic theory, an expression for the free-energy functional is obtained for Josephson-coupled layered superconductors with two order parameters corresponding to intra- and interlayer Cooper pairs. The existence of two order parameters in a system leads to the appearance of new terms in the free-energy functional known as the 'Josephson' terms and the Lifshitz invariant. Of these, the Josephson terms characterize the tunnelling of both intra- and interlayer Cooper pairs between neighbouring superconducting sheets.