DiracBilinears.jl: A package for computing Dirac bilinears in solids

DiracBilinears.jl is a Julia package for computing Dirac bilinears, which are fundamental physical quantities of electrons in relativistic quantum theory, using first-principles calculations for solids. In relativistic quantum theory, 16 independent bilinears can be defined using the four-component Dirac field. To focus on the low-energy physics typically considered in condensed matter physics, we consider the bilinears represented by the non-relativistic two-component Schrödinger field, obtained from the 1/m expansion to leading order. This package can evaluate the spatial distributions and Wannier matrix elements of the Dirac bilinears in solids quantitatively by connecting to the external first-principles calculation packages, including Quantum ESPRESSO, Wannier90, and wan2respack.