we study the coherent spin-polarized transport through a zigzag-edge graphene flake (zgf), using hubbard model in the nearest neighbor approximation within the framework of the green function’s technique and landauer formalism. the system considered consists of electrode/ (zgf)/electrode, in which the electrodes are chosen to be armchair nanoribbons. the study was performed for two types of ele...

2 Contents Introduction iii 1 Ultracold atoms on optical lattices and the dirty boson problem 1 1.

we review various ways to express the partition function of the single-band hubard model as a path integral. the emphasis is made on the derivation of the action in the integrand of the path integral and the results obtained from this approach are discussed only briefly.   since the single-band hubbard model is a pure fermionic model on the lattice and its hamiltonian is a polynomial in creatio...

The repulsive Hubbard model has been immensely useful in understanding strongly correlated electron systems, and serves as the paradigmatic of field. Despite its simplicity, it exhibits a strikingly rich phenomenology which is reminiscent that observed quantum materials. Nevertheless, much phase diagram remains controversial. Here, we review subset what known about model, based on exact results...