Transport signatures of Majorana fermions in Coulomb blockaded topological insulator nanowires

Recent theoretical works have suggested that Majorana fermions can be realized as end states in topological insulator nanowires that are proximity-coupled to a conventional superconductor. We have argued recently that the charging energy in a transistor set-up, where such a nanowire is contacted by two normal metal electrodes, can allow for the unambiguous detection of these elusive particles through measurements of the differential conductance. Characteristic Majorana transport signatures include (i) a crossover from resonant Andreev reflection (for weak interactions) to a universal halving of the Coulomb peak conductance (for strong interactions), and (ii) the appearance of magnetic-field-dependent side-band peaks at finite voltage bias in the differential conductance. The aim of the present proposal is threefold. First, we want to establish reliable theoretical predictions for the conductance in a concrete Majorana platform, namely for nanowires made out of a topological insulator (like Bi2Se3). Second, we want to study the non-local conductance and the full counting statistics in the same Majorana transistor setup, which allows to study in detail how Majorana fermions affect crossed Andreev reflection processes. In addition, such a study allows to better understand mechanisms of charge transfer in such a device. Third, we propose to analyze a system of two Majorana wires which leads to the appearance of four Majorana fermions, where the charging interaction causes different types of exotic Kondo effects. In addition, strongly non-local effects are expected to dominate transport. We will also study interference effects in this system.

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Teilprojekt zu SPP 1666:  Topologische Isolatoren: Materialien - grundlegende Eigenschaften - Strukturen für Bauelemente