First Principles Quantum Transport with Electron-vibration Interactions: A Maximally Localized Wannier Function Approach
We present an ab initio inelastic quantum transport approach based on maximally localized Wannier functions. Electronic-structure properties are calculated with density-functional theory in a planewave basis, and electron-vibration coupling strengths and vibrational properties are determined with density-functional perturbation theory. Vibration-induced inelastic transport properties are calculated with non-equilibrium Green's function techniques, which are based on localized orbitals. For this purpose we construct maximally localized Wannier functions. Our formalism is applied to investigate inelastic transport in a benzene molecular junction connected to mono-atomic carbon chains. In this benchmark system the electron-vibration self-energy is calculated either in the self-consistent Born approximation or by lowest-order perturbation theory. It is observed that upward and downward conductance steps occur, which can be understood using multi-eigenchannel scattering theory and symmetry conditions. In a second example where the mono-atomic carbon chain electrode is replaced by a (3; 3) carbon nanotube, we focus on the non-equilibrium vibration populations driven by the conducting electrons using a semi-classical rate equation.