Anomalous Thermoelectric Performance in Asymmetric Dirac Semimetal BaAgBi

Area of Science:

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

Background:

• Multiple-band degeneracy is typically linked to high thermoelectric performance.
• Understanding factors beyond degeneracy is crucial for optimizing thermoelectric materials.

Purpose of the Study:

• To investigate the thermoelectric properties of the topological semimetal BaAgBi.
• To elucidate the role of asymmetric electronic structures in its transport behavior.
• To explore strategies for enhancing thermoelectric performance in BaAgBi.

Main Methods:

• Experimental synthesis and characterization of BaAgBi.
• Transport measurements to determine Seebeck coefficient and electrical conductivity.
• Analysis of electronic band structure and relaxation time approximations.

Main Results:

• BaAgBi exhibits p-type Dirac bands with lower degeneracy, surprisingly yielding high Seebeck coefficient and electrical conductivity.
• Asymmetric electronic structures, including Dirac bands and parabolic conduction valleys, contribute to anomalous transport properties.
• An average figure of merit (ZT) of 0.42 was achieved, enhanced to 1.38 by breaking C3 symmetry.

Conclusions:

• Asymmetric electronic structures, not just band degeneracy, are key for high thermoelectric performance.
• BaAgBi serves as a model system for understanding abnormal transport in Dirac semimetals.
• Targeting asymmetric electronic features offers a new avenue for designing advanced thermoelectric materials.