Current Delivered by an STM Tip in Landauer-Büttiker Formalism

Abstract

When an STM tip is brought close to a nano sized sample then it can deliver (or draw) a current that is determined by the Landauer-Büttiker formalism in terms of the scattering matrix that gives partial local density of states. We show that, very paradoxically, the interference related term in this formula vanish in a quantum regime making semi-classical formula for injectance exact in some regime. We explicitly show how evanescent modes are responsible for this. This can have useful implications to experimentalists as semi-classical formulas are much simpler.