Quasiparticle Gaps of Nanostructures Weakly-Coupled to their Environments: The Case of C60/Metal Interfaces

ORAL

Abstract

A new approach based on density functional theory is developed to calculate charging energies and quasiparticle energy gaps of molecular systems weakly-coupled to an external environment. The approach is then applied to the case of a C60 molecule adsorbed on the Au(111) and Ag(100) surfaces. For C60/Au(111), the calculated quasiparticle gap is reduced by 2.34 eV relative to the gas-phase, consistent with recent experiments. For the more strongly-coupled C60/Ag(100) system, the predicted gap is also reduced, but differs from experiment by 0.5eV. The discrepancy is identified as being due to screening due to charge transferred from the metal to the molecule and is resolved by solving an effective Anderson Hamiltonian within the GW approximation for the carriers in the HOMO and LUMO states, which results in an extra renormalization of the gap for the Ag(100) case.

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Authors

  • Jay Sau

    Department of Physics, U C Berkeley, Material Science Divsion, LBNL

  • Jeffrey B. Neaton

    Molecular Foundry, LBNL, The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley CA-94720, Molecular Foundry, LBNL.

  • Hyoung Joon Choi

    Department of Physics and IPAP,Yonsei University, Korea, Department of Physics and IPAP, Yonsei University, Seoul, Korea, Department of Physics and IPAP, Yonsei University, Dept. of Physics and IPAP, Yonsei Univ.

  • Steven G. Louie

    Department of Physics, U C Berkeley, Material Science Divsion, LBNL

  • Marvin L. Cohen

    UC Berkeley, Lawrence Berkeley National Laboratory, Department of Physics, U C Berkeley, Material Science Divsion, LBNL, epartment of Physics, UC Berkeley, University of California, Berkeley, UC Berkeley, and LBL, UC Berkeley, UC Berkeley \& LBNL