Precursor of Charge KTB Transition in Normal and Superconducting Tunnel Junction Array

Abstract

We have measured the temperature dependence of zero-bias resistance R(T) of a two-dimensional array of small tunnel junctions with normal-statetunneling resistance of R_N=32kΩ.Both in normal and superconducting states, R(T) showedsquare-root-cusp-type behavior, typical of the chargeKosterlitz-Thouless-Berezinskii (KTB) transition, in limited temperature ranges. The transition temperature in the superconducting state, estimated from R(T), is about four times larger than that in the normal state.We consider these features to beevidence of precursor effects of the charge KTB transition.