p-type transparent superconductivity in a layered oxide

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Developing p-type transparent conducting materials with both high transparency and conductivity remains a significant challenge.
• Existing p-type transparent conductors often compromise on transparency or conductivity and do not exhibit superconductivity.

Purpose of the Study:

• To synthesize and characterize a novel p-type transparent conducting material with superconducting properties.
• To investigate the potential of Li$_{1-x}$NbO$_{2}$ as a transparent superconductor.

Main Methods:

• Epitaxial synthesis of Li$_{1-x}$NbO$_{2}$ films on cubic MgAl$_{2}$O$_{4}$ substrates via heating amorphous films.
• Stabilization of NbO$_{2}$ sheets parallel to the (111) plane.
• Characterization of electrical, optical, and superconducting properties.

Main Results:

• Successfully synthesized epitaxial Li$_{1-x}$NbO$_{2}$ films exhibiting excellent p-type transparent conductivity.
• Observed two-dimensional superconductivity below 4.2 Kelvin, triggered by hole doping via Li$^{+}$ ion deintercalation.
• Achieved approximately 77% average transmittance in the visible light spectrum for ~100-nm-thick films with carrier concentrations exceeding 10$^{22}$ cm$^{-3}$.

Conclusions:

• Li$_{1-x}$NbO$_{2}$ is identified as a novel p-type transparent superconductor.
• The material demonstrates a unique combination of high transparency, high hole carrier density, and superconductivity.
• Strongly correlated electrons in the isolated Nb 4d$_{z^2}$ band are crucial for the observed high transparency.