Coherent versus incoherent resonant tunneling in high-Tccuprates

Abstract

An analysis is performed of the resonant tunneling transport along the $c$ axis in the case where the concentration of localized resonant centers is low and the tunneling via different centers becomes incoherent. In this case the planar component of the quasimomentum is not conserved in the process of interlayer hopping. For the normal conductivity, as function of temperature and frequency, this leads only to a change of a prefactor. However, the supercurrent along the $c$ axis vanishes if the order parameter is of $d$ type and the tunneling is incoherent. An interpolation is proposed, describing a partially coherent case, when the interference terms are suppressed, but still present. A rapid decrease of the critical temperature with concentration of resonant centers and the possibility of a $\stackrel{\ensuremath{\rightarrow}}{d}s$ phase transition are predicted.