期刊
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
卷 13, 期 10, 页码 2291-2298出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.2c00379
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资金
- National Natural Science Foundation of China [52125103, 52071041, 11874356, 12104071]
In the topological semimetal BaAgBi, lower degeneracy p-type Dirac bands synergistically produce higher Seebeck coefficient and electrical conductivity. The anomalous transport phenomenon originates from asymmetric electronic structures, including complete p-type Dirac bands and additional parabolic conduction valleys.
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 ZT of 0.42 is achieved from 300 to 600 K, which can be dramatically enhanced to 1.38 via breaking the C-3v 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.
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