Enhancing the superconducting transition temperature of BaSi2 by structural tuning

Area of Science:

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

Background:

• Layered binary silicides, such as barium disilicide (BaSi2), exhibit unique structural properties.
• The sp(3) silicon atom arrangement in BaSi2's hexagonal structure results in corrugated sheets, influencing its physical properties.
• Superconductivity in materials is often linked to their structural and electronic characteristics.

Purpose of the Study:

• To investigate the superconducting phase of BaSi2.
• To explore the effect of structural modifications, specifically silicon sheet buckling, on superconductivity.
• To understand the underlying mechanisms linking structure, electronic properties, and superconductivity in BaSi2.

Main Methods:

• Joint experimental and theoretical approach.
• High-pressure synthesis to modify the buckling of silicon sheets.
• Ab initio calculations based on density-functional theory (DFT) to analyze electronic and phonon properties.

Main Results:

• Superconducting transition temperature (Tc) enhanced from 6 K to 8.9 K upon flattening of silicon planes.
• DFT calculations revealed strong correlations between silicon sheet buckling, electronic band structure, and phonon frequencies.
• Structural modifications directly impact the factors governing superconductivity.

Conclusions:

• The buckling of silicon sheets in BaSi2 is a critical parameter for tuning its superconducting properties.
• The identified mechanism of tuning superconductivity via structural control is potentially applicable to other intercalated layered superconductors.
• This study opens avenues for designing and optimizing superconductors by manipulating internal structural features.