skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Communication: Energy-dependent resonance broadening in symmetric and asymmetric molecular junctions from an ab initio non-equilibrium Green's function approach

Abstract

The electronic structure of organic-inorganic interfaces often features resonances originating from discrete molecular orbitals coupled to continuum lead states. An example is molecular junction, individual molecules bridging electrodes, where the shape and peak energy of such resonances dictate junction conductance, thermopower, I-V characteristics, and related transport properties. In molecular junctions where off-resonance coherent tunneling dominates transport, resonance peaks in the transmission function are often assumed to be Lorentzian functions with an energy-independent broadening parameter Γ. Here we define a new energy-dependent resonance broadening function, Γ(E), based on diagonalization of non-Hermitian matrices, which can describe resonances of a more complex, non-Lorentzian nature and can be decomposed into components associated with the left and right leads, respectively. We compute this quantity via an ab initio non-equilibrium Green's function (NEGF) approach based on density functional theory (DFT) for both symmetric and asymmetric molecular junctions, and show that our definition of Γ(E), when combined with Breit-Wigner formula, reproduces the transmission calculated from DFT-NEGF. Through a series of examples, we illustrate how this approach can shed new light on experiments and understanding of junction transport properties in terms of molecular orbitals.

Authors:
 [1];  [1]
  1. Molecular Foundry and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
22436531
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 141; Journal Issue: 13; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DENSITY FUNCTIONAL METHOD; ELECTRIC CONDUCTIVITY; ELECTRODES; ELECTRONIC STRUCTURE; GREEN FUNCTION; INTERFACES; MOLECULES; PEAKS; TUNNEL EFFECT

Citation Formats

Liu, Zhen-Fei, Neaton, Jeffrey B., Department of Physics, University of California, Berkeley, California 94720, and Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720. Communication: Energy-dependent resonance broadening in symmetric and asymmetric molecular junctions from an ab initio non-equilibrium Green's function approach. United States: N. p., 2014. Web. doi:10.1063/1.4897448.
Liu, Zhen-Fei, Neaton, Jeffrey B., Department of Physics, University of California, Berkeley, California 94720, & Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720. Communication: Energy-dependent resonance broadening in symmetric and asymmetric molecular junctions from an ab initio non-equilibrium Green's function approach. United States. https://doi.org/10.1063/1.4897448
Liu, Zhen-Fei, Neaton, Jeffrey B., Department of Physics, University of California, Berkeley, California 94720, and Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720. 2014. "Communication: Energy-dependent resonance broadening in symmetric and asymmetric molecular junctions from an ab initio non-equilibrium Green's function approach". United States. https://doi.org/10.1063/1.4897448.
@article{osti_22436531,
title = {Communication: Energy-dependent resonance broadening in symmetric and asymmetric molecular junctions from an ab initio non-equilibrium Green's function approach},
author = {Liu, Zhen-Fei and Neaton, Jeffrey B. and Department of Physics, University of California, Berkeley, California 94720 and Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720},
abstractNote = {The electronic structure of organic-inorganic interfaces often features resonances originating from discrete molecular orbitals coupled to continuum lead states. An example is molecular junction, individual molecules bridging electrodes, where the shape and peak energy of such resonances dictate junction conductance, thermopower, I-V characteristics, and related transport properties. In molecular junctions where off-resonance coherent tunneling dominates transport, resonance peaks in the transmission function are often assumed to be Lorentzian functions with an energy-independent broadening parameter Γ. Here we define a new energy-dependent resonance broadening function, Γ(E), based on diagonalization of non-Hermitian matrices, which can describe resonances of a more complex, non-Lorentzian nature and can be decomposed into components associated with the left and right leads, respectively. We compute this quantity via an ab initio non-equilibrium Green's function (NEGF) approach based on density functional theory (DFT) for both symmetric and asymmetric molecular junctions, and show that our definition of Γ(E), when combined with Breit-Wigner formula, reproduces the transmission calculated from DFT-NEGF. Through a series of examples, we illustrate how this approach can shed new light on experiments and understanding of junction transport properties in terms of molecular orbitals.},
doi = {10.1063/1.4897448},
url = {https://www.osti.gov/biblio/22436531}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 13,
volume = 141,
place = {United States},
year = {Tue Oct 07 00:00:00 EDT 2014},
month = {Tue Oct 07 00:00:00 EDT 2014}
}