Asymmetry in the normal-metal to high-Tcsuperconductor tunnel junction

Abstract
We show that the observed asymmetry in the IV characteristics of high-Tc material to normal-metal junctions can be explained within the resonating-valence-bond model. For a bias current with electrons moving from the superconductor to the normal metal, the current is quadratic in the bias voltage, and in the opposite case, with electrons moving from the normal metal to the superconductor, the current is linear in V.