Superconductivity in boron carbide? Clarification by low-temperature MIR/FIR spectra

Area of Science:

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

Background:

• Previous electronic structure calculations predicted metallic and superconducting properties for boron carbide (B(13)B(2)).
• These calculations were based on hypothetical crystal structures, potentially deviating from real boron carbide compositions.
• There is a need to experimentally verify the electronic properties of boron carbide.

Purpose of the Study:

• To investigate the electronic properties of boron carbide with varying compositions (B(4.3)C to B(10.37)C).
• To experimentally determine if boron carbide exhibits superconductivity.
• To analyze the optical spectra for insights into electronic band structure and states.

Main Methods:

• Optical measurements using mid-infrared/far-infrared (MIR/FIR) spectroscopy.
• Analysis of spectral data for compositions ranging from B(4.3)C to B(10.37)C.
• Temperature-dependent measurements down to 30 K.

Main Results:

• Boron carbide compositions studied demonstrated semiconducting behavior, not metallic.
• No evidence of superconductivity was observed in the experimental temperature range.
• Optical spectra provided evidence for numerous localized gap states near the valence band edge.

Conclusions:

• The experimental findings contradict theoretical predictions of metallic and superconducting properties for boron carbide.
• Boron carbide, in the studied compositions, behaves as a semiconductor.
• The presence of localized gap states is a significant finding for understanding boron carbide's electronic properties.