Probing Majorana bound states through an inhomogeneous Andreev double dot interferometer

Abstract

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

Majorana modes and Fano resonances in Aharonov-Bohm ring with topologically nontrivial superconducting bridge

“…when superconducting bridge on Fig. 1 is connected only to the left wires [35,36]) demonstrated the persistance of the stability of the Fano peaks when transport symmetry changes (from symmetric to asymmetric). Using the spinless toy model it is shown that the fundamental π/2-phase shift for tunneling into the MMs of different type prevents the collapse of Fano resonances and BIC emergence.…”

“…Finally, let us consider a limiting case of the above transport scheme by leaving only the left half of the system. In other words, in this section we turn to a Π-shaped device consisting of the LT and LB normal wires separated by the SW [35,36].…”

Probing Majorana bound states via thermoelectric transport

“…Methods to probe MBS have been proposed by one of us [8] using Aharonov-Bohm interferometry that relies on the symmetry of the non-local conductance to Aharonov-Bohm flux. Further, interference of a different sort via Andreev double-dot interferometer [9] has also been used to detect MBS. Similarly, our original idea of detecting MBS by looking at the nonlocal Aharonov-Bohm conductance [8] has been extended to look at Coulomb blockade regime in [10] or the periodicity of the oscillations in [11,12], and to experiments in [13] to detect MBS.…”