Superconductivity of structurally disordered Y₅Ir₆Sn₁₈.

Area of Science:

• Solid State Physics
• Materials Science
• Crystallography

Background:

• Y5Ir6Sn18 is a stannide compound with potential superconducting properties.
• Previous studies suggested an idealized structural model for Y5Ir6Sn18.
• Understanding the precise structure is crucial for explaining its physical properties.

Purpose of the Study:

• To investigate the structural and physical properties of Y5Ir6Sn18 single crystals.
• To clarify the structural model and its relation to superconductivity.
• To determine the superconducting mechanism and critical temperature.

Main Methods:

• Single crystal growth using Sn-flux.
• X-ray diffraction for structural analysis.
• Transmission electron microscopy (TEM) for detailed structural investigation.
• Superconducting property measurements (critical temperature).
• Theoretical electronic band structure calculations.

Main Results:

• Y5Ir6Sn18 crystallizes in a unique structure (space group Fm3̄m, a = 13.7706(1) Å) with significant disorder.
• TEM revealed a complex intergrowth of domains, indicating the X-ray diffraction model is an average description.
• The compound is a type-II superconductor with a critical temperature (Tc) of 2.1 K.
• Weak electron-phonon coupling and conventional s-wave BCS-like mechanisms govern its superconductivity.
• Electronic band structure calculations contradicted the idealized structural model.

Conclusions:

• The actual structure of Y5Ir6Sn18 is more complex than previously modeled, involving domain intergrowth.
• The observed superconductivity is conventional, consistent with BCS theory.
• Discrepancies between theoretical calculations and idealized models highlight the importance of considering structural disorder.