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Wednesday, September 28th 2022 at 2:00 PM
Topological states are recent concepts in condensed matter physics that have important implications for example in metrology, due to their robust transport properties or in topological quantum computation through the braiding of Majorana bound states. Here, we propose a novel topological Josephson junction with the normal region being a quantum spin Hall insulator. Using the BHZ model and numerical tight-binding simulations, we show that the Fraunhofer pattern in the presence of Majorana edge modes in the superconductors behaves dramatically different with respect to size and period as compared to the situation without Majorana edge modes [1]. The two regimes are connected to each other by the application of a Zeeman field. By investigating the different scattering processes in the junction by means of an analytical scattering model, we can show that the presence of Majorana edge modes can induce strong crossed Andreev reflection via the two edges (leading to non-local triplet pairing) that is otherwise strongly suppressed by virtue of the spin-momentum locking of the helical edge states. We further argue that the effect originates from a truly non-local feature of separated Majoranas that can be measured in equilibrium and at finite temperature. Together with predictions for the two-terminal conductance [2], the present setup offers unique and experimentally accessible signatures of topological superconductivity.
[1] F. Dominguez, E.G. Novik, P. Recher, to be submitted (2022).
[2] E.G. Novik, B. Trauzettel, P. Recher, Phys. Rev. B 101, 235308 (2020