Classification of Valleytronics in Thermoelectricity

Area of Science:

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

Background:

• Thermoelectric materials are crucial for energy harvesting and cooling applications.
• Traditional material design often relies on specific band structure features for enhanced thermoelectric performance.

Purpose of the Study:

• To present valleytronics as a material design tool for thermal and electrical transport.
• To investigate the influence of valleytronics parameters on thermoelectric properties.
• To develop a flowchart for understanding valleytronics' impact on the thermoelectric figure-of-merit (ZT).

Main Methods:

• Theoretical framework development for valleytronics in material design.
• Derivation and analysis of a flowchart detailing valleytronics' influence on ZT.
• Case studies on semiconductors Mg2Si, Si0.8Ge0.2, Al(x)Ga(1-x)As, and clathrate Si46-VIII.

Main Results:

• Valleytronics parameters (band degeneracy, intervalley transitions, effective mass, scattering exponent, Fermi energy) significantly impact thermoelectric properties.
• The interplay of these parameters can either enhance or degrade thermoelectric performance.
• Observed different trends in valleytronics influence across the studied semiconductors.

Conclusions:

• A degenerate multivalley bandstructure is not a universal design rule for improving ZT.
• Detailed transport studies are essential for engineering optimal bandstructures via valleytronics.
• Valleytronics provides a nuanced approach to thermoelectric material design.