Superconducting 2D cuprate with a single CuO₂ plane

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Two-dimensional (2D) materials exhibit unique quantum phenomena due to reduced dimensionality.
• High-temperature superconductivity in cuprates is strongly linked to CuO2 planes.
• Previous studies suggested essential superconductivity physics resides in two CuO2 planes.

Purpose of the Study:

• To investigate the physics of cuprates in the ultimate 2D limit using a single layer of Bi2Sr2CuO6+δ (Bi-2201).
• To explore the effects of extreme dimensionality reduction on superconducting properties.
• To tune the phase diagram of single-layer Bi-2201 and discover emergent states.

Main Methods:

• Fabrication and study of single-monolayer Bi-2201 specimens.
• Precise control of oxygenation for phase diagram tuning.
• Measurement of superconducting transition temperature and electronic properties.

Main Results:

• A ~10% reduction in optimal superconducting transition temperature was observed in the single-layer limit.
• The phase diagram of Bi-2201 was extended into new regions via controlled oxygenation.
• An anomalous metal state emerged between insulating and superconducting states near absolute zero.
• Anomalous scaling behavior with a divergent critical exponent was identified.

Conclusions:

• Dimensionality reduction significantly impacts cuprate superconductivity.
• Single-layer Bi-2201 provides a tunable platform for exploring quantum phase transitions.
• The findings shed light on the superconductor-to-insulator quantum phase transition in cuprates.