The electronic properties of cuprate ladder materials

We review the electronic properties of cuprate ladder materials, with a focus on so called 'telephone number compound' (Sr, Ca)(14)Cu24O41. This is the only ladder material which allows carrier doping and growth of single crystals. These features made investigations possible of transport anisotropy and frequency-dependent (optical) conductivity. One of the remarkable discoveries is the realization of superconductivity under high-pressure; however, analysis of transport dimensionality has suggested that the superconductivity is not due to Bose-Einstein condensation of singlet preformed pairs on the rungs, but due to cross-over from one- to two-dimensional electronic transport under pressure. This characterizes the superconductivity of 14-24-41 compound to be 'anisotropic 2-d', an extension of the category where high T-c cuprates belong to. (C) 2001 Elsevier Science B.V. All rights reserved.