KOSTERLITZ-THOULESS TRANSITION IN AN YBA2CU3O7/PRBA2CU3O7 SUPERLATTICE

A systematic study of the electrical transport properties was carried out in a YBa2Cu3O7/PrBa2Cu3O7 (48 angstrom/100 angstrom) superlattice sample. The resistance above the temperature T(KT) showed an exponential inverse-square-root temperature dependence. Below the temperature T(KT), the current-voltage characteristics in the low-current limit obeyed a power law relationship, and the universal jump of the exponent pi-K(R) from 2 to 0 was observed around T(KT). All these phenomena are consistent with the Kosterlitz-Thouless theory. The large KT transition parameter tau(KT) = (T(c0) - T(KT))/T(KT) implies an enhancement of two-dimensionality in the superlattice.