Support

Support Options

Submit a Support Ticket

 

Understanding Molecular Conduction

By Supriyo Datta

Purdue University

Published on

Abstract

datta It is common to differentiate between two ways of building a nanodevice: a topdown approach where we start from something big and chisel out what we want and a bottom-up approach where we start from something small like atoms or molecules and assemble what we want. When it comes to describing electrical resistance, the standard approach could be called a "top-down" one where we start from big complicated resistors and work our way down to molecules primarily because our understanding has evolved in this top-down fashion. But I believe it is instructive to take a bottom-up view of the subject starting from the conductance of something really small, like a molecule, and then discussing the issues that arise as we move to bigger conductors. That is what I will try to do in this tutorial lecture [1].

Remarkably enough, no serious quantum mechanics is needed to understand electrical conduction through something really small, except for unusual things like the Kondo effect that are seen only for a special range of parameters. I will (1) start with energy level diagrams, (2) show that the broadening that accompanies coupling limits the conductance to a maximum of (q^2/h) per level, (3) describe how a change in the shape of the self-consistent potential profile can turn a symmetric current-voltage characteristic into a rectifying one, (4) show that many interesting effects in molecular electronics can be understood in terms of a simple model, and (5) introduce the non-equilibrium Green's function (NEGF) formalism as a sophisticated version of this simple model with ordinary numbers replaced by appropriate matrices. Finally I will describe the distinction between the self-consistent field regime and the Coulomb blockade regime and the issues involved in modeling each of these regimes.

[1] S. Datta, "Electrical Resistance: an Atomistic View," Nanotechnology, 15, S433-S451 (2004) (pdf).

Cite this work

Researchers should cite this work as follows:

  • Supriyo Datta (2004), "Understanding Molecular Conduction," http://nanohub.org/resources/495.

    BibTex | EndNote

Time

Location

Northwestern University, Evanston, IL

Tags

nanoHUB.org, a resource for nanoscience and nanotechnology, is supported by the National Science Foundation and other funding agencies. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.