Topological isoconductance signatures in Majorana nanowires

L. S. Ricco,I. A. Shelykh,Y. Marques,J. E. Sanches,A. C. Seridonio,M. S. Figueira,M. de Souza

doi:10.1038/s41598-021-96415-3

Abstract

We consider transport properties of a hybrid device composed by a quantum dot placed between normal and superconducting reservoirs, and coupled to a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends. It is demonstrated that if highly nonlocal and nonoverlapping MBSs are formed in the system, the zero-bias Andreev conductance through the dot exhibits characteristic isoconductance profiles with the shape depending on the spin asymmetry of the coupling between the dot and the topological superconductor. Otherwise, for overlapping MBSs with less degree of nonlocality, the conductance is insensitive to the spin polarization and the isoconductance signatures disappear. This allows to propose an alternative experimental protocol for probing the nonlocality of the MBSs in Majorana nanowires.

Highlights

We consider transport properties of a hybrid device composed by a quantum dot placed between normal and superconducting reservoirs, and coupled to a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends
The proximitized nanowire is driven into the regime of unusual p-wave superconductivity and thereafter, if the value of the magnetic field exceeds the critical one, reaches the topological phase with nonoverlapping MBSs appearing at the e dges[7,8]
By analyzing the Andreev current through a quantum dot (QD) placed between metallic (N) and superconducting (S) reservoirs and coupled to a topological semiconducting nanowire (TSC) hosting MBSs (Majorana nanowire), see Fig. 1a58–61, we theoretically propose an additional protocol to differentiate between the corresponding foregoing cases of: (A) Highly nonlocal and nonoverlapping MBSs: corresponds to the case of long nanowires, L ≫ ξM, wherein L is the TSC section length and ξM is the Majorana coherence length[28]

Summary

Introduction

We consider transport properties of a hybrid device composed by a quantum dot placed between normal and superconducting reservoirs, and coupled to a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends. Other mechanisms can be responsible for the appearance of ZBPs, as for instance the formation of zero-energy Andreev bound states (ABSs)[20,21,22,23,24,25,26,27,28,29] and d isorder[17,19,27,30,31] In some cases, these topologically trivial subgap states become pinned at zero-energy for a broad range of system parameters, mimicking exactly the behavior of truly topological MBSs19,26–28,32–36. In Refs.38 and[37], it was proposed to estimate the degree of Majorana nonlocality in a Majorana

Methods

Results

Conclusion