The magnetic toroidal dipole in steric metamaterial for permittivity sensor application

Ye, Q W; Guo, Linyan; Li, M H; Liu, Y; Xiao, Bing; Yang, Helin

doi:10.1088/0031-8949/88/05/055002

Cited by 37 publications

(35 citation statements)

References 25 publications

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“…Only special structures have permanent anapole moments such as molecular nanotoroids 5,37 , ferroelectric nanostructures 38,39 , ferromagnetic structures 40 and Dy clusters (single molecule magnets) [41][42][43] . Several groups have experimentally demonstrated anapole moments in metamaterials for potential application in sensors [44][45][46] . In an external non-uniform field, toroidal spin and/or orbital currents are induced, giving rise to anapole moments and the corresponding susceptibilities can be computed.…”

Section: Introductionmentioning

confidence: 99%

Non-perturbative calculation of orbital and spin effects in molecules subject to non-uniform magnetic fields

Sen

Tellgren

2018

The Journal of Chemical Physics

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External non-uniform magnetic fields acting on molecules induce non-collinear spin densities and spin-symmetry breaking. This necessitates a general two-component Pauli spinor representation. In this paper, we report the implementation of a general Hartree-Fock method, without any spin constraints, for non-perturbative calculations with finite non-uniform fields. London atomic orbitals are used to ensure faster basis convergence as well as invariance under constant gauge shifts of the magnetic vector potential. The implementation has been applied to investigate the joint orbital and spin response to a field gradient-quantified through the anapole moments-of a set of small molecules. The relative contributions of orbital and spin-Zeeman interaction terms have been studied both theoretically and computationally. Spin effects are stronger and show a general paramagnetic behavior for closed shell molecules while orbital effects can have either direction. Basis set convergence and size effects of anapole susceptibility tensors have been reported. The relation of the mixed anapole susceptibility tensor to chirality is also demonstrated.

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Section: Introductionmentioning

confidence: 99%

Non-perturbative calculation of orbital and spin effects in molecules subject to non-uniform magnetic fields

Sen

Tellgren

2018

The Journal of Chemical Physics

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“…Various metamaterial designs have already been utilized experimentally to promote a toroidal dipole response in the microwave and optical part of the spectrum: circular apertures in a metallic screen [18], asymmetric split rings [19], split rings [20,21], and double bars [22]. In numerical simulations, also other resonator configurations [23][24][25][26][27] have shown notable toroidal dipole responses.…”

Section: Introductionmentioning

confidence: 99%

Toroidal dipole excitations in metamolecules formed by interacting plasmonic nanorods

et al. 2016

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We show how the elusive toroidal dipole moment appears as a radiative excitation eigenmode in a metamolecule resonator that is formed by pairs of plasmonic nanorods. We analyze one such nanorod configuration-a toroidal metamolecule. We find that the radiative interactions in the toroidal metamolecule can be qualitatively represented by a theoretical model based on an electric point dipole arrangement. Both a finite-size rod model and the point dipole approximation demonstrate how the toroidal dipole moment is subradiant and difficult to excite by incident light. By means of breaking the geometric symmetry of the metamolecule, the toroidal mode can be excited by linearly polarized light and appears as a Fano resonance dip in the forward scattered light. We provide simple optimization protocols for maximizing the toroidal dipole mode excitation. This opens up possibilities for simplified control and driving of metamaterial arrays consisting of toroidal dipole unit-cell resonators.

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“…The induced magnetic dipoles trace the circumference of a closed loop leading to a field structure similar to that of a toroidal solenoid. These initial observations were quickly followed by a number of works aiming to further enhance the toroidal response and suppress the contributions of competing electric and magnetic multipoles 56,57 .Planar designs were considered 58,59 (Fig. 3b) in an effort to simplify the fabrication of toroidal metamaterials.…”

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confidence: 99%

Electromagnetic toroidal excitations in matter and free space

et al. 2016

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The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion, and optical activity. Toroidal excitations also exist in free-space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal response can have important implications for the fields of photonics, sensing, energy and information. IntroductionThe interactions of electromagnetic radiation with matter underpin some of the most important technologies today -from telecommunications to information processing and data storage; from spectroscopy and imaging to light-assisted manufacturing. Our understanding and description of the electromagnetic properties of matter traditionally involves the concept of electric and magnetic dipoles, as well as their more complex combinations, known as multipoles. Introduced by Maxwell and Lorentz and later refined by Jackson and Landau, this framework, termed the multipole expansion, is central in physics and is being routinely applied in the study of optical, condensed matter, atomic, nuclear phenomena and beyond 1 . Within this framework, electromagnetic media can be represented by a set of point-like multipole sources [2][3][4][5] . The commonly used set of multipoles comprises the electric and magnetic families, which can be represented by oscillating charges and loop currents respectively. Dynamic toroidal multipoles constitute a third independent family of elementary electromagnetic sources, rather than an alternative multipole expansion or higher-order corrections to the conventional electric and magnetic multipoles (see tutorial inset I).Introduced in 1958 by Y. B. Zeldovich, toroidal moments have been considered in systems of toroidal topology (see Fig. 1) and studied in the context of nuclear 6 , atomic 7 , and molecular physics 8 , classical electrodynamics 9,10 , and solid state physics 3 . In the field of electromagnetism, in particular, a number of works have led to the development of a complete theoretical framework for toroidal electrodynamics [11][12][13][14][15] and the prediction of exotic effects, including dynamic non-radiating charge current configurations 10 and non-reciprocal interactions 9 . Following recent experimental observations of toroidal contributions in the response of materials across the electromagnetic spectrum, dyn...

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The magnetic toroidal dipole in steric metamaterial for permittivity sensor application

Cited by 37 publications

References 25 publications

Non-perturbative calculation of orbital and spin effects in molecules subject to non-uniform magnetic fields

Non-perturbative calculation of orbital and spin effects in molecules subject to non-uniform magnetic fields

Toroidal dipole excitations in metamolecules formed by interacting plasmonic nanorods

Electromagnetic toroidal excitations in matter and free space

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