Abstract
The recent experimental discovery of Josephson junctions by Szombati et al. [Nat. Phys. 12, 568 (2016)], characterized by a finite phase offset in the supercurrent, requires the same ingredients as topological superconductors, which suggests a profound connection between these two distinct phenomena. Here, we show that a quantum dot Josephson junction can serve as a qualitative indicator for topological superconductivity: microscopically, we find that the phase shift in a junction of -wave superconductors is due to the spin-orbit induced mixing of singly occupied states on the quantum dot, while for a topological superconductor junction it is due to singlet-triplet mixing. Because of this important difference, when the spin-orbit vector of the quantum dot and the external Zeeman field are orthogonal, the -wave superconductors form a Josephson junction, while the topological superconductors have a finite offset by which topological superconductivity can be distinguished from conventional superconductivity. Our prediction can be immediately tested in nanowire systems currently used for Majorana fermion experiments and thus offers a realistic approach for detecting topological bound states.
2 More- Received 23 December 2016
DOI:https://doi.org/10.1103/PhysRevB.95.195421
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