论文标题
具有近似螺钉对称系统的系统中的声子的物理
Physics of Phonons in Systems with Approximate Screw Symmetry
论文作者
论文摘要
已经对具有精确n折螺钉对称性的系统（n = 2、3、4、6）的属性进行了充分的研究，因为可以从空间组中理解它们。另一方面，已经预测了具有近似螺钉对称性的材料，例如7倍和10倍的螺钉对称性。在本文中，我们研究具有近似螺钉对称性的晶体中声子的性质，这将导致独特的新物理现象。在具有近似螺钉对称性的晶体中，我们提出了一种提取声子伪动量的信息，这是一个量子数，表征了螺钉对称性下声子模式的性质的量子数，基于以下事实，即在近似螺丝对称系统的特征螺钉中定义的量子数定义的量子数的信息。作为准备工作，我们研究了具有部分断裂的翻译对称性的一维晶体以具有扩大的单位细胞，并通过研究相邻原子之间的相对相。我们还将此方法扩展到具有近似螺钉对称性的系统，并讨论伪角动量的特性。我们将此方法应用于具有近似翻译对称性或近似螺钉对称性的候选材料上的第一原则计算结果，并显示了这种近似对称性如何在声子波函数中反映出来。
Properties of systems with exact n-fold screw symmetry (n=2, 3, 4, 6) have been well studied because they can be understood in terms of space groups. On the other hand, existence of materials with approximate screw symmetries, such as 7-fold and 10-fold screw symmetries, has been predicted. In this paper, we study properties of phonons in crystals with approximate screw symmetries, which will lead to unique and new physical phenomena. In a crystal with an approximate screw symmetry, we propose a method to extract information of pseudoangular momentum of phonons, which is a quantum number characterizing the properties of phonon modes under screw symmetry, based on the fact that the information of the quantum numbers defined under exact screw symmetry partially remains in the eigenvectors of approximate screw symmetric systems. As a preparation, we study a one-dimensional crystal with partially broken translation symmetry to have an enlarged unit cell, and we show how to extract information of a quantum number corresponding to the pseudoangular momentum, by studying a relative phase between neighboring atoms. We also extend this method to systems with an approximate screw symmetry, and discuss properties of the pseudoangular momentum. We apply this method to results of our first-principle calculations on candidate materials with an approximate translational symmetry or with an approximate screw symmetry, and show how this approximate symmetry is reflected in the phonon wavefunctions.
