Colossal Seebeck effect enhanced by quasi-ballistic phonons dragging massive electrons in FeSb2

Area of Science:

• Condensed Matter Physics
• Materials Science
• Thermoelectricity

Background:

• Phonon transport significantly influences thermoelectric material efficiency.
• Phonon-drag effect can enhance the Seebeck coefficient (S), crucial for thermoelectric devices.
• A guiding principle for designing materials that leverage the phonon-drag effect is needed.

Purpose of the Study:

• To investigate FeSb2 as a potential thermoelectric material.
• To explore the role of quasi-ballistic phonons and heavy d electrons in enhancing thermoelectric properties.
• To establish a strategy for designing phonon-drag-dominant thermoelectric materials.

Main Methods:

• Fabrication and characterization of high-purity single crystals of FeSb2.
• Systematic variation of sample size (sub-millimeter scale) to study size effects.
• Measurement of the Seebeck coefficient (S) at cryogenic temperatures.

Main Results:

• FeSb2 exhibits properties suitable for the phonon-drag effect, with quasi-ballistic phonons and heavy d electrons.
• A substantial increase in the Seebeck coefficient (S) was observed, reaching -27 mV/K at low temperatures.
• Sample size reduction significantly enhanced the Seebeck coefficient, demonstrating the importance of phonon transport.

Conclusions:

• FeSb2 is a promising thermoelectric material for low-temperature applications.
• Combining heavy electrons with ballistic phonons is a viable strategy for maximizing phonon-drag effects.
• This study provides a new avenue for designing high-performance thermoelectric materials.