Independent particle descriptions of tunneling from a many-body perspective

TL;DR

This paper investigates electron tunneling in metal-molecule-metal junctions from a many-body perspective, emphasizing the importance of overlap maximization over energy minimization in single-particle approximations.

Contribution

It introduces a novel approach to select single-particle states based on overlap with the many-body current state, challenging traditional methods like Hartree-Fock or Kohn-Sham.

Findings

Maximizing overlap yields better single-particle descriptions of tunneling.

Traditional approximations may not be optimal for open boundary systems.

A new effective potential for tunneling systems is proposed.

Abstract

Currents across thin insulators are commonly taken as single electrons moving across classically forbidden regions; this independent particle picture is well-known to describe most tunneling phenomena. Examining quantum transport from a different perspective, i.e., by explicit treatment of electron-electron interactions, we evaluate different single particle approximations with specific application to tunneling in metal-molecule-metal junctions. We find maximizing the overlap of a Slater determinant composed of single particle states to the many-body current-carrying state is more important than energy minimization for defining single particle approximations in a system with open boundary conditions. Thus the most suitable single particle effective potential is not one commonly in use by electronic structure methods, such as the Hartree-Fock or Kohn-Sham approximations.