KNIT : An open source code for quantum transport in multi-terminal systems

TL;DR

KNIT is an open-source C++/Python library that implements a recursive Green function technique for simulating quantum transport in complex multi-terminal mesoscopic systems with arbitrary geometries and Hamiltonians.

Contribution

It provides a flexible, user-friendly tool for modeling quantum transport phenomena in diverse physical systems using a generalized recursive Green function approach.

Findings

Applied to quantum Hall effect, topological insulators, graphene, superconducting systems, and ferromagnetic multilayers.

Enables calculation of conductance, noise, and local density of states.

Accessible through a simple Python interface for diverse quantum transport simulations.

Abstract

This paper is the documentation for a numerical code for quantum transport called KNIT. The KNIT library implements a generalization of the well known recursive Green function technique for a large class of multi-terminal mesoscopic systems with arbitrary geometries, topology and dimension. The systems are described by tight-biding Hamiltonians (with arbitrary internal degree of freedom like spin, electron/hole grading, orbitals...) and the calculation done within the non equilibrium Green function formalism (equivalent to the Landauer-Buttiker Scattering approach). KNIT can (and has) been applied to many different physical systems including quantum Hall effect, topological insulators, graphene ribbons, hybrid superconducting systems and ferromagnetic multilayers. KNIT main functionality is written in C++ and wrapped into Python, providing a simple and flexible interface for the user. Usual "input files" of numerical codes are replaced by small python scripts where the user builds the system and then computes whatever observable (conductance, noise, local density of states...) is needed. KNIT code can be obtained freely at the following url: http://inac.cea.fr/Pisp/xavier.waintal/KNIT.php