QUANTUM CREEP IN A BI2SR2CACU2OX SINGLE-CRYSTAL

According to the theory of quantum collective creep (QCC) of Blatter, Geshkenbein and Vinokur, the quantum creep rate is enhanced in superco nductors with short coherence length xi, high normal state resistivity rho(n), weak collective pinning and strong anisotropy. We have invest igated quantum tunneling in a single crystal of the highly anisotropic Bi2Sr2CaCu2Ox. In the configuration with the external field parallel to the c-axis we measure tunneling rates at T = 7 mK which are a facto r of 4 to 5 higher than our previous measurements in Y1Ba2Cu4Oy.