Automated quantum conductance calculations using maximally-localised Wannier functions

TL;DR

This paper introduces an automated, robust method for calculating quantum conductance in disordered quasi-one-dimensional systems using maximally-localised Wannier functions, enabling large-scale and accurate transport property analysis.

Contribution

The authors develop a novel, automated approach that transforms DFT eigenfunctions into MLWFs and manipulates Hamiltonians for efficient conductance calculations in large disordered systems.

Findings

Successfully applied to Al atomic chain with Na defect

Effective in modeling Si/Ge nanowire heterostructures

Accurately captures spin-polarised defect transport in graphene nanoribbons

Abstract

A robust, user-friendly, and automated method to determine quantum conductance in disordered quasi-one-dimensional systems is presented. The scheme relies upon an initial density- functional theory calculation in a specific geometry after which the ground-state eigenfunctions are transformed to a maximally-localised Wannier function (MLWF) basis. In this basis, our novel algorithms manipulate and partition the Hamiltonian for the calculation of coherent electronic transport properties within the Landauer-Buttiker formalism. Furthermore, we describe how short- ranged Hamiltonians in the MLWF basis can be combined to build model Hamiltonians of large (>10,000 atom) disordered systems without loss of accuracy. These automated algorithms have been implemented in the Wannier90 code[Mostofi et al, Comput. Phys. Commun. 178, 685 (2008)], which is interfaced to a number of electronic structure codes such as Quantum-ESPRESSO, AbInit, Wien2k, SIESTA and FLEUR. We apply our methods to an Al atomic chain with a Na defect, an axially heterostructured Si/Ge nanowire and to a spin-polarised defect on a zigzag graphene nanoribbon.