High-order conformal symplectic FDTD scheme

published_or_final_versionThe 2008 Asia Pacific Microwave Conference (APMC 2008), Macau, China, 16-20 December 2008. In Proceedings of the Asia Pacific Microwave Conference, 2008, p. 1-

Breaking the Space Charge Limit in Organic Solar Cells by a Novel Plasmonic-Electrical Concept

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Characterization of wave physics using the rigorous Helmholtz decomposition based on the surface integral equation

Helmholtz decomposition (HD) is a fundamental tool of vector calculus and plays an important role in electromagnetics. In this work, arbitrary vector field defined on the open or closed surface is decomposed into the sum of an irrotational (curl-free) vector field and a solenoidal (divergence-free) vector field by using the surface integral equation method. Unlike the popular loop-tree decomposition that is only a quasi-HD suitable for the circuit physics in the low frequency regime, the HD developed in this paper is rigorous and can capture both circuit and wave physics from very low frequency to high frequency regimes. The work could provide insightful physical interpretations for complex electromagnetic phenomena. © 2012 IEEE.published_or_final_versio

Magnons in Ferromagnetic Metallic Manganites

Ferromagnetic (FM) manganites, a group of likely half-metallic oxides, are of special interest not only because they are a testing ground of the classical doubleexchange interaction mechanism for the colossal magnetoresistance, but also because they exhibit an extraordinary arena of emergent phenomena. These emergent phenomena are related to the complexity associated with strong interplay between charge, spin, orbital, and lattice. In this review, we focus on the use of inelastic neutron scattering to study the spin dynamics, mainly the magnon excitations in this class of FM metallic materials. In particular, we discussed the unusual magnon softening and damping near the Brillouin zone boundary in relatively narrow band compounds with strong Jahn-Teller lattice distortion and charge/orbital correlations. The anomalous behaviors of magnons in these compounds indicate the likelihood of cooperative excitations involving spin, lattice, as well as orbital degrees of freedom.Comment: published in J. Phys.: Cond. Matt. 20 figure

Multiphysics Modeling of Plasmonic Organic Solar Cells with a Unified Finite-Difference Method

Invited Paper 13A multiphysics study carries out on plasmonic organic solar cells (OSCs) by solving Maxwell's equations and semiconductor (Poisson, drift-diffusion, and continuity) equations simultaneously with unified finite-difference framework. Regarding the Maxwell's equations, the perfectly matched layer and periodic boundary conditions are imposed at the vertical and lateral directions of OSCs to simulate the infinite air region and metallic grating electrode, respectively. In view of the semiconductor equations, the Scharfetter-Gummel scheme and semi-implicit strategy are adopted respectively in the space and time domains. To model the bulk heterojunction OSCs, the Langevin bimolecular recombination and Onsager-Braun exciton dissociation models are fully taken into account. The exciton generation rate depending on the optical absorption of the organic active material can be obtained by solving the Maxwell's equations and will be inserted into the semiconductor equations. Through the multiphysics model, we observed the increased shortcircuit current and dropped fill factor when OSCs incorporate a metallic grating anode supporting surface plasmon resonances. This work provides fundamental multiphysics modeling and understanding for plasmonic organic photovoltaics.published_or_final_versio

An efficient marching-on-in-degree solution of transient multiscale EM scattering problems

A marching-on-in-degree (MOD)-based time-domain domain decomposition method is proposed to efficiently analyze the transient electromagnetic scattering from electrically large multiscale targets. The algorithm starts with an octree that divides the whole scattering target into several subdomains. Then using the equivalence principle algorithm, each subdomain is enclosed by an equivalence sphere (ES), where both the RWG and BoR spatial basis functions are employed to expand the unknown currents. The interactions of the near-field subdomains are directly calculated by the method of moments, while the far-field interactions can be converted into the interactions of corresponding ESs. This scheme implicitly satisfies the current continuity condition, and the convergence can be accelerated as well. By harnessing the rotational symmetry of the ESs, the computational resources are reduced significantly compared with the traditional MOD method. Several numerical examples are presented to demonstrate the accuracy and efficiency of the proposed algorithm. © 2016 IEEE.postprin

Broadband absorption enhancement of organic solar cells with interstitial lattice patterned metal nanoparticles

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Artificial Perfect Electric Conductor-Perfect Magnetic Conductor Anisotropic Metasurface for Generating Orbital Angular Momentum of Microwave with Nearly Perfect Conversion Efficiency

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