Abstract
The Dirac-Bogoliubov-de Gennes equation and Blonder-Tinkham-Klapwijk theory are used to calculate the tunneling conductance and shot noise in topological insulator-based ferromagnet/ dx2−y2+idxy mixed wave superconductor (TI-based FM/ dx2−y2+idxy SC) junctions. The Andreev reflection is investigated by analyzing the conductance and shot noise. Results show that the Andreev reflection process strongly depend on the magnetic gap m in FM, the gate potential U applied to the electrode on top of SC, and the magnitude of the ratio of Δ1/Δ0 with Δ0(Δ1) the absolute of pair potential of dx2−y2(dxy) component. The specular Andreev reflection can be enhanced by m as well as U. The conventional Andreev retro-reflection, however, can be enhanced by U but be suppressed by m. Which of the two reflections dominates the tunneling phenomenon exists a turning point at m = EF where both the tunneling conductance and differential shot noise become zero. This can be used as a criterion for distinguishing between the specular Andreev reflection and the Andreev retro-reflection in thin film TI-based FM/ dx2−y2+idxy SC structures. In addition, the dx2−y2+idxy pairing symmetry as well as the magnitude of magnetic gap can be determined by the experiment of scanning tunnel spectroscopy.
Published Version
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