Quantum Transport with Spin Orbit Coupling: New Developments in TranSIESTA

TL;DR

This paper introduces a new implementation of spinor quantum transport in the TranSIESTA code, enabling accurate simulation of systems with spin-orbit coupling and non-collinear spins using first-principles methods.

Contribution

It extends TranSIESTA to incorporate full spinor wave functions, allowing for more precise modeling of topological materials and spin-dependent transport phenomena.

Findings

Successful testing on iron nanostructures showing magnetoresistance.

Transport analysis of transition metal dichalcogenide heterojunctions.

Enhanced capability for simulating spin-orbit coupled systems.

Abstract

We present the implementation of spinor quantum transport within the non-equilibrium Green's function (NEGF) code TranSIESTA based on Density Functional Theory (DFT). First-principles methods play an essential role in molecular and material modelling, and the DFT+NEGF approach has become a widely-used tool for quantum transport simulation. Exisiting (open source) DFT-based quantum transport codes either model non-equilibrium/finite-bias cases in an approximate way or rely on the collinear spin approximation. Our new implementation closes this gap and enables the TranSIESTA code to use full spinor-wave functions. Thereby it provides a method for transport simulation of topological materials and devices based on spin-orbit coupling (SOC) or non-collinear spins. These materials hold enormous potential for the development of ultra-low energy electronics urgently needed for the design of sustainable technology. The new feature is tested for relevant systems determining magnetoresistance in iron nanostructures and transport properties of a lateral transition metal dichalcogenide heterojunction.