论文标题
平面材料中的黑暗和明亮激子的离域和v $ _2 $ o $ $ _5 $的光学特性
Delocalization of dark and bright excitons in flat-band materials and the optical properties of V$_2$O$_5$
论文作者
论文摘要
具有电子的原子样定位材料中激子的最简单图片是Frenkel激子，其中电子和孔保持在一起，这与大型结合能有关。在这里，使用分层氧化物v $ _2 $ o $ _5 $的示例，我们展示了如何结合局部电荷转移激励，形成具有巨大的绑定能量的激子，但同时是一个较大的电子孔距离，我们解释了这一看似矛盾的发现。激子定位的各向异性取决于结构的局部各向异性，而激子则正延伸至由晶体结构形成的链。此外，我们表明，明亮的激子与更大的结合能和更明显的各向异性的深色激子一起进行。这些发现是通过结合第一原理多体扰动理论计算，椭圆测量实验和紧密结合建模来获得的，从而导致非常良好的一致性和一致的情况。我们的解释是一般的，可以扩展到其他材料。
The simplest picture of excitons in materials with atomic-like localization of electrons is that of Frenkel excitons, where electrons and holes stay close together, which is associated with a large binding energy. Here, using the example of the layered oxide V$_2$O$_5$ , we show how localized charge-transfer excitations combine to form excitons that also have a huge binding energy but, at the same time, a large electron-hole distance, and we explain this seemingly contradictory finding. The anisotropy of the exciton delocalization is determined by the local anisotropy of the structure, whereas the exciton extends orthogonally to the chains formed by the crystal structure. Moreover, we show that the bright exciton goes together with a dark exciton of even larger binding energy and more pronounced anisotropy. These findings are obtained by combining first principles many-body perturbation theory calculations, ellipsometry experiments, and tight binding modelling, leading to very good agreement and a consistent picture. Our explanation is general and can be extended to other materials.
