Superconducting, Insulating, and Anomalous Metallic Regimes in a Gated Two-Dimensional Semiconductor-Superconductor Array

TL;DR

This study investigates the superconductor-insulator transition in a controllable 2D semiconductor-superconductor array, revealing superconducting, metallic, and insulating regimes, and how magnetic fields influence these phases and their scaling behaviors.

Contribution

It introduces a novel, highly controllable semiconductor heterostructure array to study quantum phase transitions, providing new insights into the metallic regime and magnetic field effects.

Findings

System exhibits superconducting, metallic, and insulating regimes over nine orders of magnitude in resistance.

In-plane magnetic field suppresses the metallic regime and restores a direct superconductor-insulator transition.

Magnetic field alters the scaling exponent and improves the transition scaling.

Abstract

The superconductor-insulator transition in two dimensions has been widely investigated as a paradigmatic quantum phase transition. The topic remains controversial, however, because many experiments exhibit a metallic regime with saturating low-temperature resistance, at odds with conventional theory. Here, we explore this transition in a novel, highly controllable system, a semiconductor heterostructure with epitaxial Al, patterned to form a regular array of superconducting islands connected by a gateable quantum well. Spanning nine orders of magnitude in resistance, the system exhibits regimes of superconducting, metallic, and insulating behavior, along with signatures of flux commensurability and vortex penetration. An in-plane magnetic field eliminates the metallic regime, restoring the direct superconductor-insulator transition, and improves scaling, while strongly altering the scaling exponent.