Probing Majorana bound states through an inhomogeneous Andreev double dot interferometer

In modern experiments with hybrid superconducting (SC)/semiconducting\nnanowires the presence of zero-energy Andreev bound states (ABSs),\ncharacterized by a partial overlap of the Majorana wave functions, is a common\nproblem that significantly complicates the detection of a genuine Majorana\nbound state (MBS). In this article, taking into account spatial inhomogeneity\nof experimentally investigated nanowire samples, we study interference\ntransport features of a curved heterostructure in which two normal wires (or\narms) are separated by a superconducting wire. Since Andreev reflection on the\ntwo N/S interfaces with smoothly changing electrostatic and SC pairing\npotentials results in the emergence of bound states, the low-energy\ninterference transport is described in the framework of the model of two\nnoninteracting Andreev levels or the Andreev double quantum dot. A set of\nlimiting cases is analyzed allowing us to highlight the interference properties\nthat are unique for the different types of ABSs, such as bulk ABS,\ninhomogeneous ABS and MBS. In particular, considerable attention is paid to the\nfeatures of the Aharonov-Bohm (AB) effect. It is shown that the response of\neach state can be recognized analyzing both AB period and extrema positions of\nthe conductance oscillations which take place without any fine tuning of the\nsystem parameters.\n