It was generally assumed that weak van der Waals interactions exist between neighboring layers in the two-dimensional group-IV chalcogenides. Using PbSe as a prototypal example, however, we find additional strong coupling between the Pb-Pb layers, as evidenced by detailed analysis of the differential charge density. The coupling resembles covalent-like bond and exhibits strong harmonicity around the equilibrium distance, which can be fine tuned to obviously reduce the phonon thermal conductivity but slightly change the electronic transport of PbSe. As a consequence, a maximum ZT value of 2.5 can be realized at 900 K for the p-type system. Our work offers an effective and feasible design strategy to enhance the thermoelectric performance of similar layered structures.
Multivalley 3D Electronic Structure of PbSe from Soft-X-Ray ARPES and First-Principles Calculations
Carnegie Mellon University（卡内基梅隆大学）；International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所磁顶国际研究中心）；National Technical University “KhPI”（哈尔科夫国立理工大学）；Paul Scherrer Institut（保罗谢尔研究所）；Deutsches Elektronen-Synchrotron DESY（德国电子同步辐射中心）；University of Pittsburgh（匹兹堡大学）
Possible high thermoelectric power factor in alkali-metal-intercalated BC$_3$: anisotropic multiple valleys originating from the van Hove singularity of graphene
Identifying Highly Deformable van der Waals Layered Chalcogenides with Superior Thermoelectric Performance Using Deformability Factors and Interpretable Machine Learning
Mexican Hat and Rashba Bands in Few-Layer van der Waals Materials
各种少层二维材料的价带由布里渊区中的状态环组成。能量-动量关系具有“墨西哥帽”或Rashba色散的形式。二维态密度在带边处或附近是奇异的，带边模密度以阶跃函数的形式突变。模的大的带边密度增强了塞贝克系数、功率因数和热电优值系数ZT。电子和热电性能确定从从头计算为几层III-VI材料的GaAs，GaSe，InS，InSe，为Bi $_{2}$ Se $_{3}$，单层Bi，和双层石墨烯作为垂直场的函数。描述了层间耦合对少层III-VI材料和Bi $_{2}$ Se $_{3}$中这些性能的影响。分析模型提供了对所有这些少层材料相对一致的层相关趋势的洞察。垂直偏置的双层石墨烯可以作为测量这些效应的实验测试平台。
