标题： 范德华异质结构双层中的激子凝聚分子起源 显示英文标题

标题： Molecular Origins of Exciton Condensation in Van der Waals Heterostructure Bilayers

摘要： 最近的实验已经在双层材料中实现了激子凝聚，例如石墨烯双层和范德华异质结构MoSe$_2$-WSe$_2$，这种材料具有几乎无摩擦的能量传输潜力。 在这里，我们使用基于约化密度矩阵的先进电子结构方法，在MoSe$_2$-WSe$_2$的分子尺度片段中计算观察到激子凝聚的微观开始。 我们建立了激子凝聚的特征——粒子-空穴约化密度矩阵中存在一个大本征值——与材料中激子凝聚的实验证据之间的联系。 在异质结构双层的分子尺度片段中存在激子凝聚的“临界种子”，这为局部短程强关联效应如何导致宏观激子凝聚提供了见解。 我们发现，诸如层对齐和层间距离等分子尺度特性可以影响异质结构双层中非经典长程序的形成，这表明几何考虑对于激子凝聚材料的合理设计非常重要。 对激子凝聚微观起源的机制性见解对于设计和开发具有增强能量传输特性的新材料具有潜在意义。 显示英文摘要

摘要： Recent experiments have realized exciton condensation in bilayer materials such as graphene double layers and the van der Waals heterostructure MoSe$_2$-WSe$_2$ with the potential for nearly frictionless energy transport. Here we computationally observe the microscopic beginnings of exciton condensation in a molecular-scale fragment of MoSe$_2$-WSe$_2$, using advanced electronic structure methods based on reduced density matrices. We establish a connection between the signature of exciton condensation -- the presence of a large eigenvalue in the particle-hole reduced density matrix -- and experimental evidence of exciton condensation in the material. The presence of a "critical seed" of exciton condensation in a molecular-scale fragment of a heterostructure bilayer provides insight into how local short-range strongly correlated effects may give rise to macroscopic exciton condensation. We find that molecular-scale properties such as layer alignment and interlayer distance can impact the formation of nonclassical long-range order in heterostructure bilayers, demonstrating the importance of geometric considerations for the rational design of exciton condensate material. Mechanistic insights into the microscopic origins of exciton condensation have potential implications for the design and development of new materials with enhanced energy transport properties.