Towards a realistic transport modeling in a superconducting nanowire with Majorana fermions

TL;DR

This paper models transport in superconducting nanowires with Majorana fermions, revealing new features like energy shifts and oscillations, but finds discrepancies with experimental data suggesting other explanations for observed zero-bias peaks.

Contribution

It introduces a realistic tight-binding transport model including superconducting contacts, highlighting features absent in simpler models and analyzing their implications for Majorana detection.

Findings

Energy shift of the proximity gap signal

Enhanced visibility of the topological gap with increased spin-orbit interaction

Oscillations of the zero bias peak as a function of magnetic field

Abstract

Motivated by recent experiments searching for Majorana fermions (MFs) in hybrid semiconducting-superconducting nanostructures, we consider a realistic tight-binding model and analyze its transport behavior numerically. In particular, we take into account the presence of a superconducting contact, used in real experiments to extract the current, which is usually not included in theoretical calculations. We show that important features emerge that are absent in simpler models, such as the shift in energy of the proximity gap signal, and the enhanced visibility of the topological gap for increased spin-orbit interaction. We find oscillations of the zero bias peak as a function of the magnetic field and study them analytically. We argue that many of the experimentally observed features hint at an actual spin-orbit interaction larger than the one typically assumed. However, even taking into account all the known ingredients of the experiments and exploring many parameter regimes for MFs, we are not able to reach full agreement with the reported data. Thus, a different physical origin for the observed zero-bias peak cannot be excluded.