Nonhomogeneous charge distribution in layered high-Tc superconductors

We consider the problem of the charge distribution of holes among the various CuO2 layers in the unit cell for compounds of the type Tl2Ba2Can-1CunO2n+4. In analogy with graphite intercalation compounds, the charge distribution is strongly nonhomogeneous (for n3) with a depletion in the central layers. This result points to a special importance of the bounding layers and it provides a way to understand the observed maximum Tc as a function of n. © 1990 The American Physical Society.