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

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Two-dimensional (2D) superconductors are a rapidly developing field in condensed matter physics.
• Atomically thin layers and heterogeneous interfaces are key areas of interest for novel superconducting properties.

Purpose of the Study:

• To investigate the superconducting properties of ion-gated zirconium nitride chloride.
• To determine if superconductivity can be achieved and sustained in the ultimate two-dimensional limit.

Main Methods:

• Fabrication of an ion-gated zirconium nitride chloride surface.
• Measurement of critical temperature and upper critical fields.
• Analysis of the vortex phase diagram down to 2 Kelvin.

Main Results:

• A dome-shaped phase diagram with a maximum critical temperature of 14.8 Kelvin was observed.
• Superconductivity was confirmed to persist down to a thickness of approximately 1.8 nanometers, thinner than a single unit cell.
• A metallic state with finite resistance dominated the vortex phase diagram due to quantum creep of vortices.

Conclusions:

• Zirconium nitride chloride exhibits superconductivity in the two-dimensional limit.
• The material demonstrates unique vortex dynamics influenced by weak pinning and disorder.
• This work establishes a new platform for electric-field-induced superconductivity and the study of quantum phases in clean 2D systems.