Abstract
We employ Green’s function method for describing multiband models with magnetic impurities and apply the formalism to the problem of chromium impurities adsorbed onto a carbon nanotube. Density functional theory is used to determine the bandstructure, which is then fit to a tight-binding model to allow for the subsequent Green’s function description. Electron–electron interactions, electron–phonon coupling, and disorder scattering are all taken into account (perturbatively) with a theory that involves a cluster extension of the coherent potential approximation. We show how increasing the cluster size produces more accurate results and how the final calculations converge as a function of the cluster size. We examine the spin-polarized electrical current on the nanotube generated by the magnetic impurities adsorbed onto the nanotube surface. The spin polarization increases with both increasing concentration of chromium impurities and with increasing magnetic field. Its origin arises from the strong electron correlations generated by the Cr impurities.
Highlights
The theory for disordered materials is less well developed than the theory for periodic systems.The simplest theory of a disordered system comes from the Born approximation to scattering theory for particles moving in the periodic system with isolated scatterers due to the disorder
The method employed involves a diagrammatic expansion for the electron correlations along with a cluster-based method to treat the disorder effects
The theory is applied to a particular case of Cr dopants added to a carbon nanotube
Summary
The theory for disordered materials is less well developed than the theory for periodic systems. Slater and Koster [20,21] laid the groundwork for tight-binding model descriptions of periodic crystals, and later this approach was generalized to the case of disordered systems [22,23] This method for describing magnetic alloys begins with the effective potential in the Kohn–Sham equation [24,25], which consists of the atomic charge potential and a Pauli term, which is expressed through the magnetic field induction. The set of equations of real-time Green’s functions, along with expressions for the free energy and the electrical conductivity of disordered crystals, is based on the work presented in [31] These methods are employed to obtain our final results. In the two sections, we sketch the formalism to establish our notation and summarize the methods used
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
