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Anomalous Thermoelectric Performance in Asymmetric Dirac Semimetal BaAgBi. | LitMetric

Anomalous Thermoelectric Performance in Asymmetric Dirac Semimetal BaAgBi.

J Phys Chem Lett

Center of Quantum Materials and Devices, College of Physics, Chongqing University, Chongqing, Sichuan 401331, People's Republic of China.

Published: March 2022

AI Article Synopsis

  • Multiple-band degeneracy can enhance thermoelectric performance, but this study shows that lower degeneracy in p-type Dirac bands in BaAgBi results in better performance.
  • The unusual transport properties stem from the asymmetric electronic structures, which include high hole relaxation times and additional conduction valleys that improve charge transport.
  • A notable p-type average thermoelectric performance of 0.42 is observed, which can be increased to 1.38 by breaking symmetry, highlighting the importance of electronic structure in optimizing thermoelectric materials.

Article Abstract

Multiple-band degeneracy has been widely recognized to be beneficial for high thermoelectric performance. Here, we discover that the p-type Dirac bands with lower degeneracy synergistically produce a higher Seebeck coefficient and electrical conductivity in topological semimetal BaAgBi. The anomalous transport phenomenon intrinsically originated from the asymmetric electronic structures: (i) complete p-type Dirac bands near the Fermi level facilitate high and strong energy-dependent hole relaxation time; (ii) the presence of additional parabolic conduction valleys allows for a large density of states to accept scattered electrons, leading to an enlarged hole-electron relaxation time ratio and, thus, weakened bipolar effect. In combination with the strong lattice anharmonicity, an exceptional p-type average of 0.42 is achieved from 300 to 600 K, which can be dramatically enhanced to 1.38 via breaking the symmetry. This work uncovers the underlying mechanisms governing the abnormal transport behavior in Dirac semimetal BaAgBi and highlights the asymmetric electronic structures as target features to discover/design high-performance thermoelectric materials.

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpclett.2c00379DOI Listing

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