Transport signatures of Majorana fermions in Coulomb blockaded topological insulator nanowires

最近的理论工作表明，马约拉纳费米子可以实现为拓扑绝缘体纳米线，接近耦合到传统的超导体的端态。我们最近认为，在一个晶体管的设置，这样的纳米线是由两个正常的金属电极接触的充电能量，可以允许明确的检测这些难以捉摸的粒子通过测量的微分电导。特征马约拉纳传输签名包括（i）从共振Andreev反射（弱相互作用）到库仑峰电导（强相互作用）的普遍减半的交叉，以及（ii）在差分电导中的有限电压偏置下出现磁场依赖的边带峰。本建议的目的有三个。首先，我们希望建立可靠的理论预测电导在一个具体的马约拉纳平台，即纳米线制成的拓扑绝缘体（如Bi2Se3）。其次，我们想研究非本地电导和完整的计数统计在同一马约拉纳晶体管设置，这使得详细研究马约拉纳费米子如何影响交叉Andreev反射过程。此外，这样的研究可以更好地理解这种器件中的电荷转移机制。第三，我们建议分析一个系统的两个马约拉纳线，导致出现四个马约拉纳费米子，充电相互作用导致不同类型的异国情调的近藤效应。此外，强烈的非本地效应预计将主导运输。我们还将研究该系统中的干扰效应。

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.