Pressure dependence of Tc and electron phonon interaction in MBa2Cu3O7 systems

Abstract

Existing data for the pressure derivatives of critical temperatures Tc in the MBa2Cu3O7- y family are analyzed (M = Y, or rare earth). Using a two-dimensional BCS model, the electron-phonon coupling parameter is shown to be responsible for the increase of Tc, which varies with y in the same way as under an equivalent internal pressure. The anharmonic barium symmetrical stretching mode is compared with similar phonons in other 1-D or 2-D quasi-low-dimensional structures. A possible mechanism for large electron-phonon interaction and electron-electron pairing is proposed

The high-Tcsuperconductors: a conservative view

“…But the decrease of T, when approaching an antiferromagnetic region in the phase diagrams strongly suggests that, in contrast to organic superconductors, and analogous to normal transition metal alloys, superconductivity is due to electron-phonon couplings and weakened by antiferromagneticfluctuations and the ensuingpseudo-gap. It might be that some specific phonon mode plays a dominant role (Barisic et a1 1987, Barisic and Batistic 1989b, BaeriswylandBishop, 1987, Weber etal 1988, Besson 1989. But thevaluesof A required to explain the observed T,, of order 0.1, can be obtained by coupling via many phonon modes, as in transitional metals and alloys (Barisic et a1 1970).…”