Axis-Dependent Conduction Polarity: Design Principles and High-Throughput Discovery of Transverse Thermoelectrics

Area of Science:

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

Background:

• Axis-dependent conduction polarity (ADCP) describes semiconductor materials with distinct electron and hole transport along different crystallographic axes.
• This unique property enables functionalities like transverse thermoelectricity, but the scarcity of identified ADCP materials stems from unclear electronic design principles.
• Conventional semiconductors typically exhibit isotropic or unipolar charge transport, limiting their application in advanced electronic devices.

Purpose of the Study:

• To establish a quantitative framework defining the electronic conditions necessary for the emergence and robustness of ADCP.
• To identify novel ADCP materials and potential candidates for transverse thermoelectric applications.
• To provide chemically intuitive design rules for developing next-generation electronic materials.

Main Methods:

• Utilized a minimal two-band tight-binding model to elucidate the electronic requirements for ADCP.
• Defined key parameters: small band gap for simultaneous electron-hole transport and anisotropic carrier effective masses.
• Conducted a first-principles high-throughput screening of 4282 anisotropic narrow-gap semiconductors and metals.

Main Results:

• Identified two critical electronic conditions for ADCP: a narrow band gap and strong anisotropy in carrier effective masses.
• Discovered 361 new ADCP materials, primarily in chalcogenides, pnictides, and tetrel-based compounds, with 57 showing potential for transverse thermoelectricity.
• Analyzed representative materials (AlReGe, ZrSe3) revealing ADCP arises from anisotropic band-edge states in low-dimensional bonding networks.

Conclusions:

• The study provides a robust theoretical framework and practical design rules for discovering ADCP materials.
• The identified materials dataset accelerates the development of transverse thermoelectrics and other advanced electronic devices.
• ADCP materials offer unique transport properties crucial for future electronic and energy harvesting technologies.