Scientists Connect Thermoelectric Materials and Topological Insulators

Quantum mechanical calculations of electronic structure and transport for Bi₂Te₃ and its sister material Bi₂Te₂Se solved the long-standing puzzle of why many materials that are topological insulators are also excellent thermoelectrics. Topological insulators are a newly found class of materials where quantum mechanics and relativity in combination produce a unique conducting state on the surface. Excellent thermoelectric performance depends on a material having both high conductivity and high thermopower (electric field induced in response to a temperature difference) - a combination that does not occur in normal semiconductors.

Thermoelectric materials enable scalable direct conversion of heat to electricity in solid state devices, and have potential for recovering a portion of the energy that is lost as waste heat. ORNL researchers showed how the dual requirement of high conductivity and high thermopower can be met through iso-energy surfaces with complex shapes and large surface-to-volume ratios. This complex electronic structure is in contrast to that of typical semiconductors, which have simple spherical or ellipsoidal iso-energy surfaces. The work advances understanding of the known high performance of Bi₂Te₃, provides a design principle for discovering new thermoelectrics, and establishes a long-suspected connection between topological insulators and thermoelectrics.

H. Shi, D. Parker, M. H. Du, and D. J. Singh, “Connecting thermoelectric performance and topological insulator behavior: Bi₂Te₃ and Bi₂Te₂Se from first principles,” Physical Review Applied 3, 014004 (2015). DOI: 10.1103/PhysRevApplied.3

 

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