SPIN-FLUCTUATION GATING IN THE C-AXIS NON-DRUDE CONDUCTIVITY OF THE HIGH T-C CUPRATES

An ideal antiferromagnetic (AF) ordering of the spins of the CuO layer s of an under-doped cuprate prevents the low energy tunneling of the c harge carriers between the layers. In order to obtain a non-vanishing c-axis conductivity (sigma(c)), we invoke ground state fluctuations of the spin system. These provide a frequency-dependent,eating effect by changing the direction of the AF order parameter within one layer rel ative to that in a neighboring layer, thereby permitting some tunnelin g. The calculated sigma(c) compares favorably with experimental data i n a) being small and b) having a weak frequency dependence of distinct ly non-Drude form.