InP/GaSb core-shell nanowires: a novel hole-based platform with strong spin-orbit coupling for full-shell hybrid devices

TL;DR

This paper proposes InP/GaSb core-shell nanowires as a new platform with strong, intrinsic hole spin-orbit coupling, offering advantages for realizing Majorana zero modes in full-shell hybrid devices.

Contribution

It introduces the use of InP/GaSb core-shell nanowires with hole bands, demonstrating their robust intrinsic spin-orbit coupling suitable for topological quantum computing.

Findings

Exhibits strong, intrinsic hole spin-orbit coupling from material and geometric effects.

Shows potential for stable Majorana zero modes in hybrid devices.

Addresses limitations of previous electron-based nanowire platforms.

Abstract

Full-shell hybrid nanowires (NWs), structures comprising a superconductor shell that encapsulates a semiconductor (SM) core, have attracted considerable attention in the search for Majorana zero modes (MZMs). However, the predicted Rashba spin-orbit coupling (SOC) in the SM is too small to achieve substantial topological minigaps. In addition, the SM wavefunction spreads all across the section of the nanowire, leading typically to a finite background of trivial subgap states with which MZMs may coexist. To overcome both problems, we explore the advantages of utilizing core-shell hole-band NWs as the SM part of a full-shell hybrid, with an insulating core and an active SM shell. In particular, we consider InP/GaSb core-shell NWs, which allow to exploit the unique characteristics of the III-V compound SM valence bands. We demonstrate that they exhibit a robust hole SOC that emerges from the combination of the intrinsic spin-orbit interaction of the SM active shell and the confinement effects of the nanostructure, thus depending mainly on SM and geometrical parameters. In other words, the SOC is intrinsic and does not rely on red electric fields, which are non-tunable in a full-shell hybrid geometry. As a result, core-shell SM hole-band NWs are found to be a promising candidate to explore Majorana physics in full-hell hybrid devices, addressing several challenges in the field.