Quantum Bianisotropy Advances Light-Matter Interaction with Magnetoelectric Enhancement

The interplay between light and matter is fundamentally shaped by concepts such as bianisotropy and chirality, particularly when symmetries are broken within a material. E. O. Kamenetskii explores this interaction, demonstrating how magnetoelectric energy mediates and enhances these effects, bridging classical electromagnetics with the mechanics of metamaterials. This research reveals that magnetoelectric near fields , created by the dynamic modulation of magnetization and electric polarization within magnetic insulators , represent a non-Maxwellian field with broken spacetime symmetry. By precisely manipulating material properties at a subwavelength scale, Kamenetskii illuminates how these near fields function as a tunable environment, offering significant advances in the design of novel optical and electromagnetic devices.

Investigating and enhancing light-matter interactions forms the core of this work, a concept crucial for connecting classical electromagnetics, where bianisotropy frequently involves field non-locality, with quantum mechanics within the realm of metamaterials. The precise control of a quantum emitter’s properties at the subwavelength scale is achieved through near fields, which operate as a tunable environment. This research demonstrates that the magneto-electric (ME) near field, understood as a structure combining the effects of bianisotropy and chirality with a quantum atmosphere, represents a non-Maxwellian field exhibiting space-time symmetry breaking. Quantum ME fields originate from the dynamic modulation and topological coupling of magnetisation and electric polarisation within the metamaterial structure.

Ferrite Resonators for Quantum Magnetoelectric Coupling

Magnetoelectric, or ME, meta-atoms, subwavelength structural elements incorporating both magnetic and dielectric components within magnetic insulators, are being investigated as a means to achieve local ME coupling. This coupling is essential for defining a quantum ME energy and exploring the Feigel effect, a phenomenon related to asymmetric momentum transfer from vacuum fluctuations. Recent studies suggest that a small ferrite resonator can function as a foundational building block for metamaterials exhibiting these properties, with the ME response in a ferrite disk model characterised by violations of parity (P) and time-reversal (T) symmetry. The behaviour of these quantum meta-atoms is intrinsically linked to the localised near fields they generate and interact with, making the characterisation of these evanescent field couplings crucial.

Electromagnetic wave propagation, typically involving coupling between electric (E-field) and magnetic (H-field) vectors over a wavelength, occurs in the subwavelength region within ME materials. This raises fundamental questions about the compatibility of electromagnetism and magnetoelectricity without requiring extensions to Maxwell’s theory when examining electromagnetic wave scattering from these subwavelength resonant objects. Currently, subwavelength resonators are employed as structural elements in chiral and bianisotropic metamaterials, often modelled as LC-circuit elements and described by ME point-dipole interactions. Analyses of ME interactions within these bianisotropic metamaterials frequently utilise simple electrodynamic models incorporating electric and magnetic dipolar terms.

However, a key challenge lies in the absence of established near-field solutions to Maxwell’s equations that account for both electric and magnetic current sources linked by electromagnetic forces within a subwavelength, quasistatic region. The realisation of local coupling between electric and magnetic dipoles necessitates the violation of both spatial and temporal inversion symmetries. Existing models of bianisotropic metamaterials typically consider the ME response as a far-field characteristic determined by the geometry and arrangement of subwavelength elements, rather than the local, intrinsic ME energy of interaction. This prompts investigation into methods for locally probing the dynamic ME parameters of these structures and understanding the fundamental mechanisms driving the observed effects.

Quantized Magnetoelectric Coupling in Meta-atoms

Scientists have demonstrated the existence of quantized magnetoelectric (ME) energy within specially designed magnon-plasmon meta-atoms, representing a significant advance in light-matter interaction. Experiments revealed that these subwavelength structures, composed of ferrite disks with surface metal strips, exhibit a unique coupling between electric and magnetic properties. The team measured a complete coincidence of spectral peaks corresponding to quasistatic oscillations of both the electric and magnetic subsystems, confirming the presence of ME oscillations with distinct, quantized energy levels. This research establishes that the ME near-fields generated by these meta-atoms are non-Maxwellian, exhibiting a breaking of spacetime symmetry.

The work details how dynamic modulation and topological coupling of magnetization and electric polarization within the meta-atoms give rise to these unique fields. Measurements confirm that circulating energy within the ME fields contributes to angular momentum, resulting in a helical power flow and twisted wave propagation of electromagnetic radiation. This phenomenon stems from the density of ME energy and its influence on the electromagnetic field. Further investigation into these structures revealed the potential for asymmetric momentum transfer from the electromagnetic vacuum. Scientists theorize that the breaking of temporal and spatial symmetries within the ME structure allows for the extraction of linear momentum, specifically, a value of 7, from vacuum oscillations.

This differs fundamentally from the Casimir effect, which extracts energy, and suggests the possibility of “self-propulsion” driven by quantum vacuum fluctuations. The study highlights a crucial distinction between ME meta-atoms and conventional atoms; while both exhibit coupling between electric and magnetic energies, the mechanism in meta-atoms arises from relativistic effects and spin-orbit interaction occurring within the subwavelength structure. Researchers constructed two fundamentally different types of bianisotropic metamaterials, one utilizing LC-circuit elements for far-field responses, and another employing magnon-plasmon meta-atoms to observe localized, quantized ME energy in the near-field regions. Each particle functions as a coupled pair of magnetic and electric dipoles, described by integral-form constitutive relations for a bianisotropic material.