Superconductivity in Metastable K_1+δMo₆Se₈: A Potassium-Intercalated Chevrel Phase

Area of Science:

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

Background:

• Chevrel phases (CPs) with Mo₆X₈ structures show promise in energy and superconducting applications.
• Synthesizing new CP derivatives is difficult due to cation intercalation destabilizing the lattice, especially in selenides and tellurides.

Purpose of the Study:

• To synthesize a novel, thermodynamically metastable Chevrel phase compound, K_1+δMo₆Se₈.
• To investigate the superconducting properties of this new material.

Main Methods:

• Solid-state reaction synthesis.
• X-ray crystallography for structural determination.
• Electrical resistivity, magnetization, and specific heat measurements for characterization.

Main Results:

• Successful synthesis of K_1+δMo₆Se₈ (δ ≈ 0.37) with triclinic structure (space group P1̅).
• Observation of bulk superconductivity with a critical temperature (T_c) of 8.9 K.
• Upper critical field estimated at 26.4 T, exceeding the Pauli paramagnetic limit, suggesting multigap superconductivity.

Conclusions:

• K_1+δMo₆Se₈ expands the family of high-critical-field superconducting Chevrel phases.
• Lower-temperature solid-state reactions offer a viable route for synthesizing novel CP materials.