Anomalous Fermi-surface dependent pairing in a self-doped high-Tc superconductor

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• High-temperature superconductors (high Tc) are crucial for energy-efficient technologies.
• Understanding the complex electronic structures and pairing mechanisms in superconductors remains a significant challenge.
• Multilayer copper-oxide materials offer a platform for exploring novel superconducting phenomena.

Purpose of the Study:

• To report the discovery and characterization of a new self-doped multilayer high Tc superconductor, Ba2Ca3Cu4O8F2 (F0234).
• To investigate the distinct superconducting gap magnitudes and Fermi-surface properties of this novel material.
• To explore the implications of its electronic structure for superconductivity theories.

Main Methods:

• Synthesis and characterization of the Ba2Ca3Cu4O8F2 (F0234) compound.
• Experimental techniques to probe the superconducting gap magnitudes (e.g., ARPES, STM).
• Analysis of Fermi-surface sheets and electronic features, including van Hove singularity and magnetic scattering.

Main Results:

• Discovery of Ba2Ca3Cu4O8F2 (F0234), a self-doped superconductor with a Tc of 60 K.
• Observation of distinctly different superconducting gap magnitudes on two Fermi-surface sheets.
• Identification of both electron- and hole-doped Fermi-surface sheets within the same material.
• The larger superconducting gap is found on the electron-doped sheet, contrary to expectations.

Conclusions:

• Ba2Ca3Cu4O8F2 (F0234) represents a unique self-doped superconductor with coexisting electron- and hole-doped Fermi surfaces.
• The larger gap on the electron-doped sheet challenges established models linking superconductivity to van Hove singularities and antiferromagnetic scattering.
• This discovery opens new avenues for understanding unconventional superconductivity and designing novel superconducting materials.