Framework to identify defect-insensitive electron transport in topological semimetals

Abstract

Topological semimetals are of increasing interest to replace conventional metals for interconnects in future semiconductor chips, due to their potential to exhibit decreasing resistivity with reducing wire dimensions and a lower sensitivity to electron scattering at defects. First-principles evaluation of promising topological semimetals for interconnects typically employ non-equilibrium Green's functions (NEGF) techniques to estimate defect scattering, but such calculations for specific defect geometries are difficult to systematize and compare between disparate materials. Here, we develop an NEGF-based approach to systematically and rapidly evaluate the defect sensitivity of electron transport in materials without depending on material-specific defect geometries. Specifically, we analyze the eigen-spectrum of the transmission matrix for an incoherent ensemble of all-possible single-atom vacancy defects, which clearly reveals eigenvalues close to 1 for defect-insensitive transport modes. Applied to the leading candidates, we show that this robustness to defect scattering is extremely sensitive to surface orientation and Fermi level for each material. We find nearly-perfect insensitivity to defects only for wavevectors with single transport modes within specific Fermi level ranges in CoSi(001) and PtAl(001). Importantly, we also find high insensitivity for certain non-isolated modes in NbAs that emerge specifically due to spin-orbit coupling; these modes could not be identified previously as they were buried in the total transmission. These non-isolated modes have been buried in previous studies of total transmission, and can now be directly compared to other materials due to our standardization of defect-creation. This technique improves the state-of-the-art NEGF method and enables unbiased evaluation of future topological semimetal candidates for nanoscale interconnects.