Competing energy scales in topological superconducting heterostructures

TL;DR

This paper systematically investigates topological superconductivity in heterostructures combining Nb, Pt, and Bi2Te3, revealing how competing energy scales influence Majorana modes and the topological nature of induced superconductivity.

Contribution

It introduces a comprehensive experimental and theoretical study of engineered topological superconductors, highlighting the role of material properties and energy competition in Majorana mode realization.

Findings

Detection of zero-bias peaks linked to topological surface states.

Identification of an upper limit to the minigap size due to competing energy scales.

Theoretical model explaining the influence of material properties on topological superconductivity.

Abstract

Artificially engineered topological superconductivity has emerged as a viable route to create Majorana modes, exotic quasiparticles which have raised great expectations for storing and manipulating information in topological quantum computational schemes. The essential ingredients for their realization are spin non-degenerate metallic states proximitized to an s-wave superconductor. In this context, proximity-induced superconductivity in materials with a sizable spin-orbit coupling has been heavily investigated in recent years. Although there is convincing evidence that superconductivity may indeed be induced, it has been difficult to elucidate its topological nature. In this work, we systematically engineer an artificial topological superconductor by progressively introducing superconductivity (Nb) into metals with strong spin-orbital coupling (Pt) and 3D topological surface states (Bi2Te3). Through a longitudinal study of the character of superconducting vortices within s-wave superconducting Nb and proximity-coupled Nb/Pt and Nb/Bi2Te3, we detect the emergence of a zero-bias peak that is directly linked to the presence of topological surface states. Supported by a detailed theoretical model, our results are rationalized in terms of competing energy trends which are found to impose an upper limit to the size of the minigap separating Majorana and trivial modes, its size being ultimately linked to fundamental materials properties.