Unlocking Superconductivity in NdFeAsO via Uranium-Mediated Electron Doping.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Chemistry

Background:

• 1111-type iron-based superconductors (IBS) feature layered structures with potential for carrier doping.
• NdFeAsO is a representative IBS with alternating charge-reservoir Nd2O2 and conducting Fe2As2 layers.

Purpose of the Study:

• To investigate the effects of uranium (U) substitution at the Nd site in NdFeAsO.
• To explore U doping as a method to induce superconductivity in 1111-family IBS.

Main Methods:

• Synthesis of a series of Nd1-xUxFeAsO samples.
• Rietveld refinement of X-ray diffraction (XRD) patterns to analyze crystal structure.
• X-ray photoelectron spectroscopy (XPS) to confirm U substitution and doping type.
• Electrical transport measurements to study magnetic transitions and superconductivity.

Main Results:

• Successful synthesis of Nd1-xUxFeAsO with systematic lattice contraction upon U incorporation.
• XPS confirmed U4+ substitution for Nd3+, indicating electron doping.
• U doping suppressed the spin-density wave (SDW) transition and induced bulk superconductivity for 0.15 ≤ x ≤ 0.25.
• Optimal doping (x=0.25) yielded a superconducting critical temperature (Tc) of 47.5 K with high upper critical field (Hc2).

Conclusions:

• Uranium doping is an effective strategy for achieving superconductivity in 1111-family iron-based superconductors.
• This study provides a new avenue for tuning the electronic properties of IBS.
• The observed high Tc and Hc2 in U-doped NdFeAsO highlight its potential for advanced applications.