The 2007 Nobel Prize for physics was awarded to Dr Albert Fert and Dr Peter Grünberg for their discovery of giant magnetoresistance (GMR). GMR provides the technology that is used to read data stored on hard disks. The GMR system can be considered to represent a new class of electronic devices called “spontronics” that exploits electron spin, in addition to charge, for useful practical applications. There are many possible spintronics systems and it is a field of research that has attracted tremendous attention.
Spintronics research requires theoretical analysis and numerical modelling to understand what happens at the microscopic level. In particular, first principles atomistic modelling of quantum spin transport without using any phenomenological parameter, is desired. Such methods provide predictive power for spin transport characteristics by including atomic, chemical and material details of the nanostructure. The paperby Waldron, Liu and Guo summarizes some recent advances in the development of a formalism and its associated numerical technique for analyzing non-equilibrium quantum spin transport.The formalism is based on combining real space density functional theory (DFT) with the Keldysh non-equilibrium Green’s functions (NEGF), for which a spin non-resolved version was reported several years ago. The basic idea of the NEGF-DFT formalism is to calculate device Hamiltonian and electronic structure by DFT, deal with non-equilibrium quantum transport conditions by NEGF and account for open device boundary conditions by real space numerical procedures. Using NEGF-DFT one can now perform parameter-free calculations on nonlinear and non-equilibrium quantum spin transport from atomic first principles. For a specific example of Fe/MgO/Fe trilayer nanostructure well studied at equilibrium, we demonstrate several important technical issues of analyzing non-equilibrium properties of this magnetic tunnel junction and compare them with corresponding experimental data. We believe that the newly developed NEGF-DFT quantum spin transport package will be useful for many quantitative calculations of spintronic systems.
Spintronics research requires theoretical analysis and numerical modelling to understand what happens at the microscopic level. In particular, first principles atomistic modelling of quantum spin transport without using any phenomenological parameter, is desired. Such methods provide predictive power for spin transport characteristics by including atomic, chemical and material details of the nanostructure. The paperby Waldron, Liu and Guo summarizes some recent advances in the development of a formalism and its associated numerical technique for analyzing non-equilibrium quantum spin transport.The formalism is based on combining real space density functional theory (DFT) with the Keldysh non-equilibrium Green’s functions (NEGF), for which a spin non-resolved version was reported several years ago. The basic idea of the NEGF-DFT formalism is to calculate device Hamiltonian and electronic structure by DFT, deal with non-equilibrium quantum transport conditions by NEGF and account for open device boundary conditions by real space numerical procedures. Using NEGF-DFT one can now perform parameter-free calculations on nonlinear and non-equilibrium quantum spin transport from atomic first principles. For a specific example of Fe/MgO/Fe trilayer nanostructure well studied at equilibrium, we demonstrate several important technical issues of analyzing non-equilibrium properties of this magnetic tunnel junction and compare them with corresponding experimental data. We believe that the newly developed NEGF-DFT quantum spin transport package will be useful for many quantitative calculations of spintronic systems.
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