Conductance of a Quantum Point Contact in the presence of a Scanning Probe Microscope Tip

TL;DR

This paper investigates how a scanning probe microscope tip affects electron conductance in a quantum point contact, revealing conductance modulation and fringe patterns that depend on tip position, temperature, and voltage.

Contribution

It introduces a recursive Green's function approach to model conductance changes caused by a scanning tip in quantum point contacts, aligning with experimental observations.

Findings

Conductance of specific channels decreases with tip at certain positions.

Coherent fringes are smoothed out by increased temperature or voltage.

Results match experimental data by Topinka et al.

Abstract

Using the recursive Green's function technique, we study the coherent electron conductance of a quantum point contact in the presence of a scanning probe microscope tip. Images of the coherent fringe inside a quantum point contact for different widths are obtained. It is found that the conductance of a specific channel is reduced while other channels are not affected as long as the tip is located at the positions correspending to that channel. Moreover, the coherent fringe is smoothed out by increasing the temperature or the voltage across the device. Our results are consistent with the experiments reported by Topinka et al.[Science 289, 2323 (2000)].