Supercurrent modulated by magnetization in a composite topological superconductor junction.

We report a theoretical study of the supercurrent flowing in a composite topological superconductor (TS) junction, where a magnetized quantum dot is considered in between the two TS leads. Based on the tight-binding model and the Keldysh Green's function method, we found that the magnetization (m) in the dot can significantly modify the current-phase relationship, and a nonzero supercurrent flows at zero superconducting phase gradient when m has a component perpendicular to both the external magnetic field h and the pseudomagnetic field Bsoc from the spin-orbit coupling. The induced zero-phase supercurrent can be modulated substantially by both the magnitude and the direction of m, and takes its maximum value at the critical magnetic field of the topological phase transition. Our findings might provide an experimentally simple and accessible scheme for the detection of Majorana fermions.