A Magnetic Monopole Antenna
Reynier, B., X. Yang, B. Gallas, S. Bidault, and M. Mivelle
ACS Photonics 10, no. 9, 3070-3076 (2023)
Abstract: Magnetic monopoles are hypothetical particles which, similar to the electric monopoles that generate electric fields, are at the origin of magnetic fields. Despite many efforts, to date, these theoretical particles have yet to be observed. Nevertheless, many systems or physical phenomena mimic the behavior of magnetic monopoles. Here, we propose a new type of photonic nanoantenna behaving as a radiating magnetic monopole. We demonstrate that a half-nanoslit in a semi-infinite gold layer generates a single pole of enhanced magnetic field at the nanoscale and that this single pole radiates efficiently in the far field. We also introduce an effective magnetic charge using Gauss’s law of magnetism, in analogy to the electric charge, which further highlights the monopolar behavior of this new antenna. Finally, we show that different plasmonic and metallic materials can provide magnetic monopole antennas covering the visible-to-near infrared range, even down to GHz frequencies. This original antenna concept opens the way to a new model system to study magnetic monopoles and a new optical magnetic field source to study “magnetic light-matter coupling.” Furthermore, it shows potential applications at lower frequencies, such as in magnetic resonance imaging.
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Measuring Dirac cones in a brick-wall lattice microwave metamaterial
Li, B., S. Yves, A. Delory, S. Liu, M. Fink, and F. Lemoult
Physical Review B 108, no. 9 (2023)
Abstract: The intriguing discovery of bidimensional structures in solid-state physics has motivated the seeking of their analogs in many fields. In this paper, we propose a general scheme to achieve Dirac cones in the microwave domain. It is based on a bidimensional locally resonant metamaterial ruled by a tight-binding Hamiltonian with asymmetric coupling. By specifically controlling the hopping links between meta-atoms, the Dirac cones can be moved in the first Brillouin zone. A proof of this assertion is performed theoretically, numerically, and experimentally using a brick-wall lattice of resonant metallic wires. The results directly evidence that the crystalline description of a subwavelength-scaled microwave system provides a really convenient tabletop platform for investigating the tempting challenges offered in solid-state physics.
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Real-time detection of virus antibody interaction by label-free common-path interferometry
Alhaddad, S., H. Bey, O. Thouvenin, P. Boulanger, C. Boccara, M. Boccara, and I. Izeddin
Biophysical Reports 3, no. 3, 100119 (2023)
Abstract: Viruses have a profound influence on all forms of life, motivating the development of rapid and minimally invasive methods for virus detection. In this study, we present a novel methodology that enables quantitative measurement of the interaction between individual biotic nanoparticles and antibodies in solution. Our approach employs a label-free, full-field common-path interferometric technique to detect and track biotic nanoparticles and their interactions with antibodies. It is based on the interferometric detection of light scattered by viruses in aqueous samples for the detection of individual viruses. We employ single-particle tracking analysis to characterize the size and properties of the detected nanoparticles, and to monitor the changes in their diffusive mobility resulting from interactions. To validate the sensitivity of our detection approach, we distinguish between particles having identical diffusion coefficients but different scattering signals, using DNA-loaded and DNA-devoid capsids of the Escherichia coli T5 virus phage. In addition, we have been able to monitor, in real time, the interaction between the bacteriophage T5 and purified antibodies targeting its major capsid protein pb8, as well as between the phage SPP1 and nonpurified anti-SPP1 antibodies present in rabbit serum. Interestingly, these virus-antibody interactions are observed within minutes. Finally, by estimating the number of viral particles interacting with antibodies at different concentrations, we successfully quantify the dissociation constant Kd of the virus-antibody reaction using single-particle tracking analysis.
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