Detecting Majorana modes through Josephson junction ring-quantum dot hybrid architectures

Abstract

Unequivocal signatures of Majorana zero energy modes in condensed matter systems and manipulation of the associated electron parity states are highly sought after for fundamental reasons as well as for the prospect of topological quantum computing. In this paper, we demonstrate that a ring of Josephson coupled topological superconducting islands threaded by magnetic flux and attached to a quantum dot acts as an excellent parity-controlled probe of Majorana mode physics. As a function of flux threading through the ring, standard Josephson coupling yields a Φ 0 = h/(2e) periodic features corresponding to 2π phase difference periodicity. In contrast, Majorana mode assisted tunneling provides additional features with 2Φ 0 (4π phase difference) periodicity, associated with single electron processes. We find that increasing the number of islands in the ring enhances the visibility of the desired 4π periodic components in the groundstate energy. Moreover as a unique characterization tool, tuning the occupation energy of the quantum dot allows controlled groundstate parity changes in the ring, enabling a toggling between Φ 0 and 2Φ 0 periodicity.

Accessing different topological classes and types of Majorana edge states in coupled superconducting platforms using perturbations

“…The initial proposals were based on the detection of the zero-bias conduc-tance peaks in nanowires which had the possibility of containing the trivial zero-energy Andreev bound states [24][25][26][27][28] . In a couple of recent works, observation of 4π periodic Josephson current was observed across different geometric junctions of topological superconductors, which is another compelling signature of current being carried by single electron processes, contrary to that in conventional superconductors [29][30][31][32][33] . Even this procedure is often hindered by quasi-particle poisoning, especially in experiments under stationary equilibrium conditions, and one needs to be sure that this 4π-periodicity is not caused by Landau-Zener transitions between topologically trivial subgap states 34 .…”