Critical temperatures of superconductors with low dimensionality

The superconducting state of a two-dimensional electron gas in the presence of a subgroup with a high density of states (DOS) is studied. It is shown that in this system a strong electron-phonon coupling arises; in addition, an important role is played by two-dimensional plasmons. The theory is applied to a description of the properties of the recently discovered class of materials with high $T_c$. Their low dimensionality and the presence of groups with high DOS makes these materials unique.