Transmission Amplitude through a Coulomb blockaded Majorana Wire

We study electronic transport through a Coulomb blockaded superconducting Rashba wire in the co-tunneling regime between conductance resonances. Embedding such a wire into one arm of an electron interferometer allows to study the amplitude for coherent transmission. Varying an external Zeeman field allows to tune the wire into a topological regime, where localized Majorana zero modes are formed at both ends of the wire. In this topological phase, the nonlocal transport through Majorana zero modes is the dominant mechanism and gives rise to a maximum in the transmission amplitude as a function of Zeeman field, whose height is proportional to the wire length. On the other hand, for tunneling through a generic extended state or through a pair of Andreev bound states, the transmission amplitude is independent of wire length. Hence, the Zeeman field and length dependence of the transmission amplitude are unique signatures for the presence of Majorana zero modes. Our results allow an interpretation of the recent experimental results [1].

[1] A. M. Whiticar et al., Nature Communications 11, 3212 (2020).