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arXiv 1405.4685cond-mat.mtrl-sci
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高方向电子态能带工程在体半导体中的低维输运和大热电功率因子

Low-Dimensional Transport and Large Thermoelectric Power Factors in Bulk Semiconductors by Band Engineering of Highly Directional Electronic States

Daniel I. Bilc, Geoffroy Hautier, David Waroquiers, Gian-Marco Rignanese, Philippe Ghosez

摘要:

热电技术有望解决能源问题,但其开发仍然受到低效率的阻碍。到目前为止,通过降低热导率已经取得了很大的改善,但通过最大化功率因数的改善较少。后者对能带结构提出了明显矛盾的要求:窄的能量分布和低的有效质量。纳米结构中的量子限制或共振态的引入被认为是解决这一悖论的可能方案,但成功有限。在这里,我们提出了一个原始的方法来满足这两个要求,在散装半导体。它利用一些轨道的高度方向性来设计能带结构,并产生一种类似于纳米结构中目标的低维传输,同时保持各向同性特性。使用第一性原理计算,理论概念证明在Fe $_2$ YZ Heusler化合物,产生的功率因数4-5倍,在室温下比经典热电。我们的发现是完全通用的,并合理化的替代化合物具有类似的行为搜索。除了热电,这些可能也与电子、超导或光伏应用有关。

英文摘要:

Thermoelectrics are promising to address energy issues but their exploitation is still hampered by low efficiencies. So far, much improvement has been achieved by reducing the thermal conductivity but less by maximizing the power factor. The latter imposes apparently conflicting requirements on the band structure: a narrow energy distribution and a low effective mass. Quantum confinement in nanostructures or the introduction of resonant states were suggested as possible solutions to this paradox but with limited success. Here, we propose an original approach to fulfill both requirements in bulk semiconductors. It exploits the highly-directional character of some orbitals to engineer the band-structure and produce a type of low-dimensional transport similar to that targeted in nanostructures, while retaining isotropic properties. Using first-principles calculations, the theoretical concept is demonstrated in Fe$_2$YZ Heusler compounds, yielding power factors 4-5 times larger than in classical thermoelectrics at room temperature. Our findings are totally generic and rationalize the search of alternative compounds with a similar behavior. Beyond thermoelectricity, these might be relevant also in the context of electronic, superconducting or photovoltaic applications.

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