Willatzen Morten, Lew Yan Voon Lok C, Gandi Appala Naidu, Schwingenschlögl Udo
Department of Photonics Engineering, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark.
College of Science and Mathematics, The University of West Georgia, 1601 Maple St, Carrollton, GA 30117. USA.
Beilstein J Nanotechnol. 2017 Jun 30;8:1345-1356. doi: 10.3762/bjnano.8.136. eCollection 2017.
A general three-dimensional continuum model of phonons in two-dimensional materials is developed. Our first-principles derivation includes full consideration of the lattice anisotropy and flexural modes perpendicular to the layers and can thus be applied to any two-dimensional material. In this paper, we use the model to not only compare the phonon spectra among the group-IV materials but also to study whether these phonons differ from those of a compound material such as molybdenum disulfide. The origin of quadratic modes is clarified. Mode coupling for both graphene and silicene is obtained, contrary to previous works. Our model allows us to predict the existence of confined optical phonon modes for the group-IV materials but not for molybdenum disulfide. A comparison of the long-wavelength modes to density-functional results is included.
建立了二维材料中声子的通用三维连续体模型。我们的第一性原理推导充分考虑了晶格各向异性以及垂直于层的弯曲模式，因此可应用于任何二维材料。在本文中，我们使用该模型不仅比较了IV族材料之间的声子谱，还研究了这些声子是否与诸如二硫化钼之类的复合材料的声子不同。阐明了二次模式的起源。与之前的工作相反，得到了石墨烯和硅烯的模式耦合。我们的模型使我们能够预测IV族材料中受限光学声子模式的存在，但不能预测二硫化钼中的受限光学声子模式。还包括了长波长模式与密度泛函结果的比较。
