Efficient Atomic Self-Interaction Correction Scheme for Nonequilibrium Quantum Transport

Density-functional theory calculations of electronic transport based on local exchange and correlation functionals contain self-interaction errors. As a consequence, insulating molecules in weak contact with metallic electrodes erroneously form highly conducting junctions. Here we present a fully self-consistent and still computationally undemanding self-interaction correction scheme that overcomes these limitations. The method is implemented in the transport code Smeagol and applied to the prototypical case of benzene molecules and gold electrodes. The Kohn-Sham highest occupied molecular orbital now reproduces closely the negative of the molecular ionization potential and is moved away from the gold Fermi energy. This leads to a drastic reduction of the low-bias current in much better agreement with experiments.

Figure 1

Schematic diagram of a metal-molecule-metal junction. (a) A scattering region is sandwiched between two current or voltage probes kept at the chemical potentials ${\mu }_1$ and ${\mu }_2$. (b) Energy level lineup. (c) Transmission coefficient as a function of energy.

Figure 2

BDT (a) and BDMT (b) molecules attached to the hollow site of the Au (111) surface. The sulfur-surface distance is 1.9 Å. Color code: $\mathrm{Au}=\mathrm{\text{yellow}}(\mathrm{\text{or light gray}})$, $\mathrm{C}=\mathrm{\text{black}}$, $\mathrm{S}=\mathrm{\text{dark yellow}}(\mathrm{\text{or gray}})$, $\mathrm{H}=\mathrm{\text{blue}}(\mathrm{\text{or dark gray}})$.

Figure 3

Transport properties of a BDT molecule attached to the gold (111) hollow site. The left plots correspond to LDA and the right ones to ASIC. The upper panels are the DOS of the S and C $\pi$ orbitals [(a),(b)], the middle are the transmission coefficients as a function of energy for various bias [(c),(d)], and the lower are the $I\mathrm{\text{−}}V$ curves. Panel (f) is a zoom of (e) and compares our results with experiments from Ref. [7]. The vertical lines in (c) and (d) mark the bias window.

Figure 4

Transport properties of a BDMT molecule attached to the gold (111) hollow site. The left panels correspond to LDA and the right ones to ASIC. The upper panels are the DOS of the S and C $\pi$ orbitals [(a),(b)], the middle are the transmission coefficients as a function of energy for various bias [(c),(d)], and the lower are the $I\mathrm{\text{−}}V$ curves. Panel (f) is a zoom of (e) and compares our results with experiments from Ref. [7]. The vertical lines in (c) and (d) mark the bias window.