Type-I superconductivity in KBi₂ single crystals

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Understanding the fundamental properties of novel superconducting materials is crucial for advancing condensed matter physics.
• Potassium bismuthide (KBi2) is a material system where superconductivity has been recently investigated.

Purpose of the Study:

• To comprehensively investigate the superconducting and normal state properties of KBi2 single crystals.
• To determine the type of superconductivity and key superconducting parameters of KBi2.

Main Methods:

• Detailed measurements of transport, magnetic, and thermodynamic properties.
• Theoretical calculations were performed to complement experimental findings.
• Specific heat measurements were used to analyze phase transitions.

Main Results:

• KBi2 exhibits metallic behavior in the normal state and superconductivity below a critical temperature (T(c)) of 3.573 K.
• The material displays low critical fields, typical magnetization isotherms of a type-I superconductor, and a small Ginzburg-Landau parameter (κ(GL) = 0.611).
• A field-induced crossover from a second- to first-order phase transition was observed in specific heat measurements.

Conclusions:

• KBi2 is definitively identified as a type-I superconductor.
• The thermodynamic critical field (H(c)) for KBi2 was determined to be 234.3(3) Oe.
• The findings provide valuable insights into the nature of superconductivity in KBi2.