Dependence of superconducting gap on hole doping level in La2-xSrxCuO4

We re-examined the superconducting gap 2 Delta(0) of La2-xSrxCuO4 (x = 0.18 and 0.2) by using tunneling techniques. The gap magnitude 2 Delta(0) is in agreement with k(B)T(max), where k(B)T(max) will give an effective exchang e energy between Cu spins, indicating that the pairing mechanism would be m agnetic in origin. The resistivity decreases more rapidly with lowering T b elow a temperature T*. We also report that T* agrees with the mean-field tr ansition temperature T-c(MF), given by the relation 2 Delta(0) = 4.3 k(B)T( c)(MF). (C) 1998 Elsevier Science Ltd. All rights reserved.