We investigate exemplary the longitudinal optical (LO) mode order in compounds with a plasmon or plasmon-like phonon mode and additional phonon modes. When the oscillator strength of the plasmon or plasmon-like mode is gradually increased, a reordering of the modes takes place. Since it is not possible in crystals with orthorhombic or higher symmetry that a LO mode crosses a transverse optical (TO) mode's position, this reordering takes place via mode hybridization. During this mode hybridization, the plasmon or plasmon-like LO mode gradually becomes the originally higher situated LO mode while the latter morphs into the former. As a consequence, inner (LO-TO) and an outer (TO-LO) mode pair is formed. These insights can be readily transferred to other semiconductors or many mode materials with reststrahlen bands, as long as their dielectric tensor can be (partly) diagonalized, and allow easily correct mode assignments.

我们研究具有等离激元或等离激元的声子模式和其他声子模式的化合物中的示例性纵向光学（LO）模式顺序。当等离激元或类似等离激元模式的振荡器强度逐渐增加时，将发生模式的重新排序。由于在具有正交或更高对称性的晶体中，LO模式不可能跨越横向光学（TO）模式的位置，因此这种重新排序是通过模式杂交进行的。在这种模式杂交过程中，等离激元或类似等离激元的LO模式逐渐变成原来位置较高的LO模式，而后者则演变为前者。结果，形成内部（LO-TO）模式和外部（TO-LO）模式对。这些见解可以很容易地转移到其他半导体或具有reststrahlen带的多种模式材料中，