Fast & Furious TBpack-Sneg

The modern literature on condensed matter physics favours presentation of the tight-binding model with a tool of quantum field theory referred to as the second quatization. In the second quantization approach a quantum system, that is normally a collection of particles confined by some potential, is fully described by its energy levels and the corresponding occupation numbers. In this so-called occupation number representation of quantum mechanics, one operates with creation and annihilation operators of a particle. In some areas such as quantum magnetism or superconductivity this approach forms a "first principles" basis, while in the electronic structure theory it can be avoided. In both cases, however, one can end up with a construction of the matrix Hamiltonian based on the same principles of the tight-binding model. In this version, TBpack has incorporated Sneg library by Rok Zitko as an independent component. Sneg library allows one to easily define operators and perform transformations within the second quantization formalism. Having this component at hand within TBpack facilitates a smooth pedagogical introduction into a range of topics originating from the modern condensed matter physics.