Designing Nanomagnet Arrays for Topological Nanowires in Si

TL;DR

This paper explores the design of nanomagnet arrays on silicon to induce topological states for quantum computing, offering a silicon-based alternative to traditional materials with strong spin-orbit coupling.

Contribution

It introduces a detailed simulation framework for nanomagnet arrays on silicon, providing new design rules and an experimentally feasible configuration for topological nanowires.

Findings

Nanomagnet arrays can induce an artificial spin-orbit gap in silicon.

Design guidelines for nanomagnet arrangements to optimize topological states.

A practical design with single polarization magnets is proposed.

Abstract

Recent interest in topological quantum computing has driven research into topological nanowires, one-dimensional quantum wires that support topological modes including Majorana fermions. Most topological nanowire designs rely on materials with strong spin-orbit coupling, such as InAs or InSb, used in combination with superconductors. It would be advantageous to fabricate topological nanowires using Si owing to its mature technology. However, the intrinsic spin-orbit coupling in Si is weak. One approach that could circumvent this material deficiency is to rotate the electron spins using nanomagnets. Here, we perform detailed simulations of realistic Si/SiGe systems with an artificial spin-orbit gap induced by a nanomagnet array. Most of our results are also generalizable to other nanomagnet-based topological nanowire designs. By studying several concrete examples, we gain insight into the effects of nanomagnet arrays, leading to design rules and guidelines. Finally, we present an experimentally realizable design using magnets with a single polarization.