Structure and bonding of superconducting LaC2

Area of Science:

• Solid State Physics
• Materials Science
• Superconductivity

Background:

• Lanthanum carbide (LaC2) is a material with potential superconducting properties.
• Understanding the behavior of binary carbides is crucial for developing new superconducting materials.

Purpose of the Study:

• To synthesize and characterize polycrystalline lanthanum carbide (LaC2).
• To investigate the superconducting properties and structural behavior of LaC2.
• To compare the electronic structure and properties of LaC2 with YC2.

Main Methods:

• Synthesis of polycrystalline LaC2 samples.
• X-ray and neutron powder diffraction for structural analysis.
• Magnetic susceptibility and heat capacity measurements to determine superconducting properties.
• Ab initio electronic structure calculations.

Main Results:

• Superconductivity observed in LaC2 below approximately 1.8 K, dependent on preparation conditions.
• LaC2 identified as a weak-coupling BCS-type superconductor based on heat capacity analysis.
• No evidence of structural phase transitions down to 4 K.
• Observed negative thermal expansion of the c lattice parameter below approximately 50 K.
• Calculated electronic structure of LaC2 and compared it with YC2.

Conclusions:

• LaC2 is a weak-coupling BCS-type superconductor.
• The material exhibits unique thermal expansion properties.
• The study provides insights into the structure-property relationships of lanthanum and yttrium carbides.