Unconventional behavior of the scattering times in high-T-c cuprates

We have measured the anisotropic charge dynamics in the 90-K phase of YBa2Cu3Oy, and have found that the out-of-plane scattering time is more than five times shorter than the in-plane scattering time. Another anomaly is the rapid enhancement of the in-plane scattering time below T-c. Our magneto-thermopower measurement has revealed that the enhancement also occurs in the mixed state. These two features are never observed in other layered superconductors, such as organic BEDT salts or Sr2RuO4; thus, they can be direct evidence for the non-Fermi-liquid behavior of high-T-c cuprates.