C-AXIS CONDUCTIVITY IN THE NORMAL-STATE OF CUPRATE SUPERCONDUCTORS

The c-axis optical conductivity and de resistivity are calculated with in the t-J model assuming that the interlayer hopping is incoherent. U se is made of numerical results for spectral functions recently obtain ed with the finite-temperature Lanczos method for finite two-dimension al systems. In the optimally doped regime we find an anomalous relaxat ion rate tau(c)(-1) proportional to omega + xi(c)T and rho(c)(T) propo rtional to rho(ab)(T), suggesting a common relaxation mechanism for in tra- and interlayer transport. At low doping a pseudogap opening in th e density of states appears to be responsible for a semimetalliclike b ehavior of rho(c)(T). [S0031-9007(98)07458-4].