Real-space method for first-principles electron-transport calculations: self-energy terms of electrodes for large systems

TL;DR

This paper introduces a fast, stable real-space numerical method to accurately compute self-energy terms in large-scale first-principles electron-transport calculations, improving efficiency and stability.

Contribution

The authors develop a novel technique using orthogonal complement vectors to enhance accuracy and computational stability in self-energy calculations for large systems.

Findings

Efficiently computed self-energy terms for large systems.

Observed resonance scattering in silicene with Stone-Wales defect.

Identified different sensitivities of conduction channels to defects.

Abstract

We present a fast and stable numerical technique to obtain the self-energy terms of electrodes for first-principles electron-transport calculations. Although first-principles calculations based on the real-space finite-difference method are advantageous for execution on massively parallel computers, large-scale transport calculations are hampered by the computational cost and numerical instability of the computation of the self-energy terms. Using the orthogonal complement vectors of the space spanned by the generalized Bloch waves that actually contribute to transport phenomena, the computational accuracy of transport properties is significantly improved with a moderate computational cost. To demonstrate the efficiency of the present technique, the electron-transport properties of a Stone-Wales (SW) defect in graphene and silicene are examined. The resonance scattering of the SW defect is observed in the conductance spectrum of silicene since the $\sigma^\ast$ state of silicene lies near the Fermi energy. In addition, we found that one conduction channel is sensitive to a defect near the Fermi energy, while the other channel is hardly affected. This characteristic behavior of the conduction channels is interpreted in terms of the bonding network between the bilattices of the honeycomb structure in the formation of the SW defect. The present technique enables us to distinguish the different behaviors of the two conduction channels in graphene and silicene owing to its excellent accuracy.