Evidence of conventional superconductivity in La-Ba-Cu-O compounds

First-principles methods are applied to investigate the electronic structure and electron-phonon coupling in the end-point members (x = 0 and x = 1) of the new high-transition-temperature T(c) superconductor La(2-x)Ba(x)CuO4 and their counterpart cubic perovskites La(1-x)Ba(x)CuO3. Alloying with Ba (x = 1) induces nonrigid-band changes in the Cu and O density of states, but the Cu charge state changes rather little. The calculated McMillan-Hopfield parameter eta coupled with soft phonon modes provides a strong electron-phonon interaction lambda of about 2.5 that can account for the high T(c) of about 30-40 K in these systems.