In-plane selective area InSb\u2013Al nanowire quantum networks

Roy L M Op Het Veld,Mihir Pendharkar,Joon Sue Lee,Di Xu,Chuyao Tong,Bart Hesselmann,Zhibiao Hao ,Stan Peters ,Sebastian Koelling,Michiel W A De Moor,Jason J Jung ,Vanessa Schaller,Kiefer Vermeulen,Leo Miglio,C J Palmstrøm ,Qingzhen Wang,Andrey Sarikov,Marcel A Verheijen,Leo P Kouwenhoven,Anna Marzegalli,Jouri Bommer ,Erik P A M Bakkers

doi:10.1038/s42005-020-0324-4

Abstract

Strong spin–orbit semiconductor nanowires coupled to a superconductor are predicted to host Majorana zero modes. Exchange (braiding) operations of Majorana modes form the logical gates of a topological quantum computer and require a network of nanowires. Here, we utilize an in-plane selective area growth technique for InSb–Al semiconductor–superconductor nanowire networks. Transport channels, free from extended defects, in InSb nanowire networks are realized on insulating, but heavily mismatched InP (111)B substrates by full relaxation of the lattice mismatch at the nanowire/substrate interface and nucleation of a complete network from a single nucleation site by optimizing the surface diffusion length of the adatoms. Essential quantum transport phenomena for topological quantum computing are demonstrated in these structures including phase-coherence lengths exceeding several micrometers with Aharonov–Bohm oscillations up to five harmonics and a hard superconducting gap accompanied by 2e-periodic Coulomb oscillations with an Al-based Cooper pair island integrated in the nanowire network.

Highlights

Strong spin–orbit semiconductor nanowires coupled to a superconductor are predicted to host Majorana zero modes
Merging of VLS nanowires inevitably forms a widening of the nanowire diameter at and around the junction with a 75% chance of a defect forming at the junction, which negatively affects the onedimensionality of the system[8]
A more scalable approach, would be to use an in-plane selective area growth (SAG) technique, that relies on a template or mask to selectively grow one semiconductor material on top of another[13,14,15,16,17,18,19]

Summary

Introduction

Strong spin–orbit semiconductor nanowires coupled to a superconductor are predicted to host Majorana zero modes. We demonstrate an in-plane SAG technique for scalable and high-quality InSb nanowire networks, which shows all the relevant quantum transport properties (e.g., long coherence length and excellentinduced superconducting properties) necessary for topological qubits. When these nuclei merge by lateral growth, an inclined defect is formed at the interface; details of the atomic structure of such a defect can be found in Supplementary Fig. 1.

Results

Conclusion