低维体系中的量子挠曲电
Quantum Flexoelectricity in Low Dimensional Systems
摘要：
在表面和界面处的对称性破坏以及在纳米级系统中支持大应变梯度的能力使得能够实现新形式的机电耦合。在这里，我们引入量子挠曲电的概念，当非极性量子系统的机械变形导致净偶极矩的出现，从而线性机电耦合与局部曲率成比例时，表现出这种现象。这一概念在碳系统中得到了说明，包括聚乙炔和纳米石墨带。使用密度泛函理论计算系统由多达400个原子，我们确定的挠曲电系数的顺序为~ 0.1 E，与线性理论的预测一致。讨论了量子挠曲电在机电器件应用和碳基材料物理方面的意义。
英文摘要：
Symmetry breaking at surfaces and interfaces and the capability to support large strain gradients in nanoscale systems enable new forms of electromechanical coupling. Here we introduce the concept of quantum flexoelectricity, a phenomenon that is manifested when the mechanical deformation of non-polar quantum systems results in the emergence of net dipole moments and hence linear electromechanical coupling proportional to local curvature. The concept is illustrated in carbon systems, including polyacetylene and nano graphitic ribbons. Using density functional theory calculations for systems made of up to 400 atoms, we determine the flexoelectric coefficients to be of the order of ~ 0.1 e, in agreement with the prediction of linear theory. The implications of quantum flexoelectricity on electromechanical device applications, and physics of carbon based materials are discussed.
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