The Superconductivity in Bi-Doped BaFe₂As₂ Single Crystals

Area of Science:

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

Background:

• BaFe2As2 is a parent compound for iron-based superconductors.
• Understanding the effects of doping on its physical properties is crucial for discovering new superconducting materials.
• Bismuth (Bi) doping has not been previously explored in BaFe2As2 single crystals.

Purpose of the Study:

• To synthesize and characterize Bi-doped BaFe2As2 single crystals for the first time.
• To investigate the impact of Bi doping on the crystal structure, electronic properties, and magnetic ordering.
• To explore the relationship between non-Fermi liquid behavior and superconductivity in this novel system.

Main Methods:

• Single crystal growth via flux method.
• X-ray diffraction (XRD) for structural analysis.
• Resistivity and magnetic susceptibility measurements for electronic and magnetic property investigations.

Main Results:

• Successful synthesis of high-quality Bi-doped BaFe2As2 single crystals.
• XRD revealed an expansion of lattice parameter c with Bi doping, indicating a negative pressure effect.
• Observed a Fermi liquid (FL) to non-Fermi liquid (NFL) crossover.
• Detected three distinct superconducting transitions (SC I, SC II, SC III) at various Bi concentrations.
• Magnetic susceptibility suggested SC I and SC III are filamentary, while SC II is bulk superconductivity around 7 K.

Conclusions:

• Bi doping in BaFe2As2 induces a negative pressure effect and leads to a FL-NFL crossover.
• The NFL behavior is closely associated with the emergence of superconductivity.
• Multiple superconducting phases with different characteristics (filamentary vs. bulk) are present in Bi-doped BaFe2As2.