Summa Francesco Ferdinando, Monaco Guglielmo, Zanasi Riccardo, Lazzeretti Paolo
Dipartimento di Chimica e Biologia "A. Zambelli," Università degli studi di Salerno, via Giovanni Paolo II 132, Fisciano 84084, SA, Italy.
J Chem Phys. 2022 Feb 7;156(5):054106. doi: 10.1063/5.0082731.
The continuous search for metamaterials with special properties, suitable for new technological applications, is presently being driven by a preceding theoretical development, which took place after the introduction of new physical entities, anapole and a family of toroidal multipoles, having a border in common with those considered in the more familiar electric and magnetic multipole expansions. The related concept of toroidization, i.e., toroidal moment per unit volume, has been advocated in analogy to electric polarization and magnetization operated by electromagnetic fields and should be considered on the same footing regarding its relevance and practicality for understanding certain properties, e.g., ferrotoroidicity in condensed matter physics, and for rationalizing the behavior of charge-current distributions that neither radiate nor interact with external fields in classical and quantum electrodynamics. Toroidizability, i.e., the ability of sustaining toroidal moments, can also be defined by an analogy with electric polarizability and magnetizability. The present study shows that such a property is general and characterizes atoms and molecules and that the optical electric field of a light beam induces an oscillating anapole moment, i.e., the superposition of toroidal moment with an electric dipole moment. However, values of anapole polarizabilities induced by monochromatic light, estimated by time-dependent perturbation theory for rare gas atoms and a few molecules, are quite small and possibly hard to detect experimentally.
对具有特殊性质、适用于新技术应用的超材料的持续探索，目前是由先前的理论发展推动的。这一理论发展是在引入新的物理实体——无偶极和一族环形多极子之后发生的，它们与更常见的电和磁多极展开中所考虑的实体有共同的边界。环形化的相关概念，即单位体积的环形矩，是类似于由电磁场产生的电极化和磁化而提出的，就其对于理解某些性质（例如凝聚态物理中的铁环形性）的相关性和实用性，以及对于合理化在经典和量子电动力学中既不辐射也不与外部场相互作用的电荷 - 电流分布的行为而言，应该在相同的基础上加以考虑。环形可激发性，即维持环形矩的能力，也可以通过与电极化率和磁导率的类比来定义。本研究表明，这样一种性质是普遍的，并且表征原子和分子，并且光束的光电场会诱导一个振荡的无偶极矩，即环形矩与电偶极矩的叠加。然而，通过含时微扰理论对稀有气体原子和一些分子估计的单色光诱导的无偶极极化率的值相当小，可能很难通过实验检测到。
