Enhanced and modulable induced superconducting gap and effective Land\'e g-factor in Pb-InSb hybrid devices

TL;DR

This paper demonstrates that Pb-InSb hybrid devices exhibit a large, tunable superconducting gap and high effective g-factors, enhancing their potential for topological quantum computing compared to traditional Al-based systems.

Contribution

It introduces Pb-based hybrid devices with a large, tunable superconducting gap and strong spin-orbit coupling, surpassing Al-based systems in key properties for topological quantum applications.

Findings

Pb hybrid devices have a superconducting gap exceeding 1.4 meV.

The gap can be electrostatically tuned from maximum to nearly zero.

Effective g-factors up to 76 were observed, indicating strong SOC.

Abstract

The hybrid system of a conventional superconductor (SC) on a semiconductor (SM) nanowire with strong spin-orbit coupling (SOC) represents a promising platform for achieving topological superconductivity and Majorana zero modes (MZMs) towards topological quantum computation. While aluminum (Al)-based hybrid nanowire devices have been widely utilized, their limited superconducting gap and intrinsic weak SOC as well as small Land\'e g-factor may hinder future experimental advancements. In contrast, we demonstrate that lead (Pb)-based hybrid quantum devices exhibit a remarkably large and hard proximity-induced superconducting gap, exceeding that of Al by an order of magnitude. By exploiting electrostatic gating to modulate wavefunction distribution and SC-SM interfacial coupling, this gap can be continuously tuned from its maximum value (~1.4 meV, matching the bulk Pb gap) down to nearly zero while maintaining the hardness. Furthermore, magnetic-field-dependent measurements reveal a radial evolution of the gap structure with anti-crossing feature, indicative of strong SOC and huge effective g-factors up to 76. These findings underscore the superior functionality of Pb-based hybrid systems, significantly advancing their potential for realizing and stabilizing MZMs and the further scalable topological quantum architectures.