Stub model for charge transport through a quantum dot connected to noncollinear ferromagnets

A stub model is introduced to describe the charge transport properties of a system consisting of an arbitrary number of noncollinear ferromagnetic or normal reservoirs coupled nonideally to a normal metal chaotic cavity. We characterize the contacts by a reduced set of parameters which can be used to express the average value of any charge-transfer cumulant. Explicit expressions of this set of parameters are given for the cases of ideal ballistic contacts and tunnel junctions. The average conductance and shot-noise power of a two terminal FNF device with noncollinear ferromagnetic reservoirs are calculated analytically via an extended diagrammatic method which allows for the importation of all diagrams of the corresponding NNN system. We observe that the Fano factor exhibits a transition between monotonic and nonmonotonic behaviors as a function of the reservoir's relative magnetization angle. A diagram of this transition in the plane of the polarization parameters is shown. With straightforward modifications, our scheme paves the way for efficient calculations of the average value of an arbitrary cumulant of the charge-transfer statistics in hybrid devices along with its quantum corrections.