XTRANS: An electron transport package for current distribution and magnetic field in helical nanostructures

In this paper, the algorithms of non-equilibrium Green’s function (NEGF) approach for electron transport properties of nanostructures which are implemented in XTRANS, the package developed by our group, are described. Incorporated with the tight-binding method, this package not only can compute the regular PBC structure, but also is capable of studying those systems which possess no translational symmetry but helical symmetry. It selects the appropriate symmetry to minimize the computation cost if the system is subject to both symmetries. It also involves the utility of visualizing the current distribution across the nanostructure in forms of “bond current”, with which we developed a fast and accurate procedure to compute the induced magnetic field and further the inductance. To demonstrate the application, we also calculate multiple examples of nanostructures with either translational or helical symmetry, and reveal their distinctive electric and magnetic properties. To our knowledge, these features have never been available in previous ready-to-use packages for electron transport.