Abstract
We theoretically investigate spin polarized conductance through nanojunctions made by magnetic domains in a thin films of three dimensional ferromagnetic topological insulator (TI) as a quantum anomalous Hall insulator. Writing of magnetic domains is now feasible in recent experiments. Ferromagnetism induced in such materials can control topological phase of the band structure and as consequence, configuration of the states in each band. By means of band analysis, it is demonstrated that in topologically non-trivial bands with non-zero Chern number, there exists a change in spin dominant states among Brillouin zone while spin polarization of trivial bands shows dominant of one spin type. Indeed, there is an interplay between topological invariant of the band spectrum and contribution of the spin states in conductance. We show that in-plane magnetization or structure inversion asymmetry result in a k-dependent parity configuration of surface states in ultrathin film topological insulator. In the conduction and valence bands, a nearly perfect spin polarized conductance is found in a nanojunction composed of anti-parallel magnetic domains which is mediated by a layer under application of in-plane magnetization or perpendicular applied bias. This spin polarized region is extendable with the magnetization. To the sake of completeness, proposed polarization in conductance was also supported by interpretation based on spin and parity local density of states along the interfaces of magnetic domain walls. Analysis of the spin-parity states sheds light to the quantum transport through magnetically doped TI thin-film’s nanojunctions with different mass terms.
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