Metallic ground state in an ion-gated two-dimensional superconductor

TL;DR

This study demonstrates that ion-gated ZrNCl remains superconducting at the 2D limit with a metallic vortex phase, revealing a metallic ground state in a clean, atomically thin superconductor driven by electric fields.

Contribution

It provides the first evidence of a metallic ground state in an ion-gated 2D superconductor, with detailed analysis of vortex dynamics and superconducting thickness.

Findings

Superconductivity persists down to ~1.8 nm thickness.

A metallic vortex phase with finite resistance is observed at low temperatures.

Electric-field-induced superconductivity offers a new platform for quantum phase exploration.

Abstract

Recently emerging two-dimensional (2D) superconductors in atomically thin layers and at heterogeneous interfaces are attracting growing interest in condensed matter physics. Here, we report that ion-gated ZrNCl surface, exhibiting a dome-shaped phase diagram with a maximum critical temperature of 14.8 kelvin, behaves as a superconductor persisting to the 2D limit. The superconducting thickness estimated from the upper critical fields is ~ 1.8 nanometers, which is thinner than one-unit-cell. The majority of the vortex phase diagram down to 2 kelvin is occupied by a metallic state with a finite resistance, owing to the quantum creep of vortices caused by extremely weak pinning and diminishing disorder. Our findings highlight the potential of electric-field-induced superconductivity, establishing a new platform for accessing quantum phases in clean 2D superconductors.