Theory of Optical Nonlocality in Polar Dielectrics

Scaleability of dielectric susceptibility $ε_{zz}$ with the number of layers and additivity of ferroelectric polarization in van der Waals semiconductors

We study the dielectric response of few layered crystals of various transition metal dichalcogenides (TMDs) and hexagonal Boron Nitride (hBN). We showed that the out-of-plane polarizability of a multilayer crystal (which characterizes response to the external displacement field) scales linearly with the number of layers, $α_{zz}^{NL} =N α_{zz}^{1L}$, independently of the stacking configuration in the film. We also established additivity of ferroelectric polarizations of consecutive interfaces in case when such interfaces have broken inversion symmetry. Then we used the obtained data of monolay…

Polarizabilities of complex individual dielectric or plasmonic nanostructures

When the sizes of photonic nanoparticles are much smaller than the excitation wavelength, their optical response can be efficiently described with a series of polarizability tensors. Here, we propose a universal method to extract the different components of the response tensors associated with small plasmonic or dielectric particles. We demonstrate that the optical response can be faithfully approximated, as long as the effective dipole is not induced by retardation effects, hence do not depend on the phase of the illumination. We show that the conventional approximation breaks down for a phas…

Predicting polarization and nonlinear dielectric response of arbitrary perovskite superlattice sequences

We carry out first-principles calculations of the nonlinear dielectric response of short-period ferroelectric superlattices. We compute and store not only the total polarization, but also the Wannier-based polarizations of individual atomic layers, as a function of electric displacement field, and use this information to construct a model capable of predicting the nonlinear dielectric response of an arbitrary superlattice sequence. We demonstrate the successful application of our approach to superlattices composed of SrTiO$_3$, CaTiO$_3$, and BaTiO$_3$ layers.

Nonlocal effects in singular plasmonic metasurfaces

A local model of the dielectric response of a metal predicts that singular surfaces, such as sharp-edged structures, have a continuous absorption spectrum and extreme concentration of energy at the singularity. Here we show that nonlocality drastically alters this picture: the spectrum is now discrete and energy concentration, though still substantial, is greatly reduced.

两个极性介电材料纳米间隙间极端近场热输运的原子模拟

Atomistic modeling of extreme near-field heat transport across nanogaps between two polar dielectric materials

本研究通过分子动力学模拟MgO纳米间隙热输运，发现与连续介质理论存在显著偏差，归因于非局域介电响应和声子隧穿，并揭示了晶格非谐性的重要影响。

Mode structure and polaritonic contributions to the Casimir effect in a magneto-dielectric cavity

We present a full analysis of the mode spectrum in a cavity formed by two parallel plates, one of which is a magneto-dielectric, e.g. a metamaterial, while the other one is metallic, and obtain dispersion relations in closed form. The optical properties of the cavity walls are described in terms of realistic models for the effective permittivity and the permeability. Surface polaritons, i.e. electromagnetic modes that have at least partly an evanescent character, are shown to dominate the Casimir interaction at small separations. We analyze in detail the s-polarized polaritons, which are a cha…

Topological Surface-plasmon-polaritons on Corrugated Metal-dielectric Surfaces

We study topological surface-plasmon-polaritons at optical frequencies in diffraction gratings formed by bipartite corrugated metal-dielectric gratings. To do so we implement the theory as developed in Della Valle and Longhi to describe the amplitude of the field by an emergent Schrödinger-like equation. The tri-harmonic grating generates a bipartite Kronig-Penney model. Topologically protected localised modes are then predicted to occur at the edges of the grating and at defects formed by the combination of two mirror antisymmetric corrugations, whose bulk invariant is a step-wise varying Zak…

非局域激子光学响应对单层过渡金属硫族化合物面内激子极化激元的影响

Influence of nonlocal excitonic optical response on in-plane exciton polaritons supported by monolayer transition-metal dichalcogenides

本研究发展非局域激子光学响应微观理论，研究hBN封装单层WS₂中面内激子极化激元，发现空间非局域性使色散向低波矢移动，产生更平滑且横向延伸的近场分布，并可通过hBN厚度调控多模式贡献。

Operative Approach to Quantum Electrodynamics in Dispersive Dielectric Objects Based on a Polarization Modal Expansion

In this paper we deal with the macroscopic electromagnetic response of a finite size dispersive dielectric object, in unbounded space, in the framework of quantum electrodynamics using the Heisenberg picture. We apply a Hopfield type scheme to account for the dispersion and dissipation of the matter. We provide a general expression of the polarization density field operator as functions of the initial conditions of the matter field operators and of the electromagnetic field operators. It is a linear functional whose kernel is a linear expression of the impulse response of the dielectric object…