Thermoelectric (TE) materials, with the ability to convert heat directly to electricity, have attracted worldwide increasing attention due to the strong urge for clean energy today. However conventional TE devices suffer from the low conversion efficiency for decades due to the trade-off between TE parameters. Novel quantum materials such as topological insulators with unique boundary states protected topologically against backscattering offer a new way for designing high-performance TE devices. Here we demonstrate that topological insulator nanoribbons, which exhibit unconventional TE behaviors, can greatly improve the TE efficiency. As an example, we calculate the TE properties of the ZrTe₅ nanoribbon through the Boltzmann transport theory with the electronic bands and the thermal conductivity obtained from ab initio calculations. The dramatic difference in the scattering intensity between the in-gap topological edge states and the bulk states originates several unusual TE behaviors: (I) The electrical to electronic thermal conductivity ratio can be several times larger than that predicted by the Wiedemann-Franz law. (II) The reduced Seebeck coefficient shows an anomalous opposite sign to that of normal semiconductors with the magnitude much larger than unity. (III) By properly introducing defects, the thermal conductivity can be significantly reduced without noticeably deteriorating the electrical conductivity. (IV) Under appropriate strain, the electrical to electronic thermal conductivity ratio could be tens of times larger due to the bulk gap narrowing. These results indicate that a figure of merit larger than ten is highly likely.

能够将热量直接转换为电能的热电（TE）材料由于当今对清洁能源的强烈需求而吸引了全世界越来越多的关注。然而，由于TE参数之间的折衷，常规的TE装置遭受了数十年的低转换效率。新型量子材料（例如具有独特边界状态的拓扑绝缘体）在拓扑上受到了保护，可以防止反向散射，这为设计高性能TE器件提供了一种新途径。在这里，我们证明拓扑绝缘体纳米带表现出非常规的TE行为，可以大大提高TE效率。例如，我们通过玻尔兹曼输运理论计算ZrTe ₅纳米带的TE特性，并通过电子带和热导率计算得出。从头开始计算。间隙内拓扑边缘状态和本体状态之间的散射强度的巨大差异引发了几种不寻常的TE行为：（I）电气电子热导率比Wiedemann-Franz定律所预测的大几倍。（II）降低的塞贝克系数显示出与正常半导体相反的异常符号，其幅度远大于1。（III）通过适当地引入缺陷，可以在不显着降低电导率的情况下显着降低热导率。（IV）在适当的应变下，由于体积间隙变窄，电导热导率可能会大几十倍。这些结果表明，品质因数大于10的可能性很高。