Transition voltage spectroscopy in vacuum break junction: The standard tunneling barrier model and beyond

Abstract

AbstractRecent experiments on transition voltage (Vt) spectroscopy in mechanically controllable vacuum break junctions have been interpreted theoretically by using a Simmons WKB‐type approach of the transport by tunneling based on the standard vacuum barrier picture (work function + source‐drain bias + charge images). In the first part of the paper, we present an analysis demonstrating the inconsistencies of that approach. Then, we report detailed results obtained by exactly solving the Schrödinger equation, which show that the standard tunneling barrier model fails to describe the experimental vacuum transition voltage spectroscopy (TVS) data. This indicates that the physical description within that model is incomplete. In the attempt to go beyond the standard barrier model, we report results demonstrating that the inclusion of electron states at the electrodes' surface significantly improves the agreement with experiment. This applies both to the d‐dependence of Vt and to the jump in the linear conductance when approaching the atomic contact limit.