Unconventional lattice dynamics in few-layer h-BN and indium iodide crystals

• 来源期刊: 中国物理B（英文版）
• 关键词: flexural mode quadratic dispersion long-range interaction frequency redshift dielectric screen-ing
• 年，卷（期）: 2018,（8）
• 页码范围: 425-432
• 页数: 8页
• 语种: 英文
• DOI: 10.1088/1674-1056/27/8/086301

摘要

Unusual quadratic dispersion of flexural vibrational mode and red-shift of Raman shift of in-plane mode with increas-ing layer-number are quite common and interesting in low-dimensional materials, but their physical origins still remain open questions. Combining ab initio density functional theory calculations with the empirical force-constant model, we study the lattice dynamics of two typical two-dimensional (2D) systems, few-layer h-BN and indium iodide (InI). We found that the unusual quadratic dispersion of flexural mode frequency on wave vector may be comprehended based on the com-petition between atomic interactions of different neighbors. Long-range interaction plays an essential role in determining the dynamic stability of the 2D systems. The frequency red-shift of in-plane Raman-active mode from monolayer to bulk arises mainly from the reduced long-range interaction due to the increasing screening effect.