Two-dimensional epitaxial superconductor-semiconductor heterostructures: A platform for topological superconducting networks

TLDR

Topological superconductivity research relies on new material combinations that merge superconductivity, low carrier density, and strong spin‑orbit coupling, and theory predicts that a 1D semiconductor with strong SOC proximitized by a superconductor hosts Majorana modes, while recent epitaxial Al/InAs nanowires have demonstrated high‑quality, transparent interfaces and a hard induced gap. The authors aim to establish a 2D InAs/InGaAs heterostructure with epitaxial Al as a platform for gate‑controlled networks of topological superconductors hosting Majorana zero modes. They successfully fabricated a 2D InAs/InGaAs heterostructure with epitaxial Al that exhibits planar S‑Sm interfaces and transport properties comparable to epitaxial nanowires, enabling gate‑controlled Josephson junctions and highly transparent interfaces suitable for extended topological superconducting networks.

Abstract

Progress in the emergent field of topological superconductivity relies on synthesis of new material combinations, combining superconductivity, low density, and spin-orbit coupling (SOC). For example, theory [1-4] indicates that the interface between a one-dimensional (1D) semiconductor (Sm) with strong SOC and a superconductor (S) hosts Majorana modes with nontrivial topological properties [5-8]. Recently, epitaxial growth of Al on InAs nanowires was shown to yield a high quality S-Sm system with uniformly transparent interfaces [9] and a hard induced gap, indicted by strongly suppressed sub gap tunneling conductance [10]. Here we report the realization of a two-dimensional (2D) InAs/InGaAs heterostructure with epitaxial Al, yielding a planar S-Sm system with structural and transport characteristics as good as the epitaxial wires. The realization of 2D epitaxial S-Sm systems represent a significant advance over wires, allowing extended networks via top-down processing. Among numerous potential applications, this new material system can serve as a platform for complex networks of topological superconductors with gate-controlled Majorana zero modes [1-4]. We demonstrate gateable Josephson junctions and a highly transparent 2D S-Sm interface based on the product of excess current and normal state resistance.