Transport signatures of Majorana fermions in Coulomb blockaded topological insulator nanowires

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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.