Eth Honggerberg Inst Theoret Phys Ch-8093 Zurich Switzerland
Max Planck Inst Festkorperforsch D-70569 Stuttgart Germany

We study the electronic structure of the ladder compounds SrCu2O3 and Sr14-xCaxCu24O41. Our local-density approximation calculations for SrCu2O3 give similar Cu 3d bands near the Fermi energy as reported for Sr14-xCaxCu24O41. The hopping parameters estimated by fitting these bands show a strong anisotropy between the t(perpendicular to) and t(parallel to) intraladder hopping and small interladder hopping. A downfolding method shows that this anisotropy arises from the ladder structure. The conductivity perpendicular to the ladders is computed assuming incoherent tunneling giving a value close to experiment.

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Physical Review B, 57 R12655-12658 Rapid Comm., 1998.