Are topological insulators promising thermoelectrics?

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Physics

Background:

• Topological insulators (TIs) possess unique electronic properties due to their surface states.
• Existing research often focuses on TI surface states for thermoelectric (TE) applications, overlooking bulk properties.
• Current operating conditions for TE devices differ significantly from those where TI surface states are most effective.

Purpose of the Study:

• To investigate the role of bulk band structure in the thermoelectric performance of topological insulators (TIs).
• To determine if TIs can outperform normal insulators as thermoelectric materials under relevant conditions.
• To identify key properties of TIs that enhance thermoelectric efficiency.

Main Methods:

• High-throughput transport calculations using density functional theory (DFT).
• Development of theoretical models based on Boltzmann transport theory.
• Analysis of band structure properties, specifically band inversion and warping.

Main Results:

• Optimized TIs generally outperform normal insulators within the same structural class.
• Thermoelectric performance correlates positively with the strength of band inversion.
• Band inversion-driven warping is identified as the mechanism enhancing TE performance by reducing transport mass and increasing valley degeneracy.

Conclusions:

• Band inversion strength is a critical factor for the thermoelectric performance of TIs.
• Warping, a consequence of band inversion, significantly boosts TE efficiency.
• Alloying and strain engineering are proposed as strategies to tune band inversion and improve TE performance in TIs, positioning them as viable candidates for TE applications.