arXiv subjects

4

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4 recordsLinked to original sources

arXiv2023

Tunable Strong Magnon-Magnon Coupling in Two-Dimensional Array of Diamond Shaped Ferromagnetic Nanodots

Hybrid magnonics involving coupling between magnons and different quantum particles have been extensively studied during past few years for varied interests including quantum electrodynamics. In such systems, magnons in magnetic materials with high spin density are utilized where the coupling strength is collectively enhanced by the square root of the number of spins to overcome the weaker coupling between individual spins and the microwave field. However, achievement of strong magnon-magnon coupling in a confined nanomagnets would be essential for on-chip integration of such hybrid systems. Here, through intensive study of interaction between different magnon modes in a Ni80Fe20 (Py) nanodot array, we demonstrate that the intermodal coupling can approach the strong coupling regime with coupling strength up to 0.82 GHz and cooperativity of 2.51. Micromagnetic simulations reveal that the intermodal coupling is mediated by the exchange field inside each nanodot. The coupling strength could be continuously tuned by varying the bias field strength and orientation, opening routes for external control over hybrid magnonic systems. These findings could greatly enrich the rapidly evolving field of quantum magnonics.

cond-mat.mes-hall↗

arXiv2020

High-Q transparency band in all-dielectric metasurfaces induced by a quasi bound state in the continuum

Bound states in the continuum (BICs) emerge throughout Physics as leaky/resonant modes that remain however highly localized. They have attracted much attention in Optics and Photonics, and especially in metasurfaces, i.e. planar arrays of sub-wavelength meta-atoms. One of their most outstanding feature is the arbitrarily large Q-factors they induce upon approaching the BIC condition, which we exploit here to achieve a narrow transparency band. We first show how to shift a canonical BIC in an all-dielectric metasurface, consisting of high-refractive disks exhibiting in- and out-of-plane magnetic dipole (MD) resonances, by tuning the periodicity of the array. By means of our coupled electric/magnetic dipole formulation, we show analytically that when the quasi-BIC overlaps with the broad (in-plane MD) resonance, a full transparency band emerges with diverging Q-factor upon approaching the BIC condition in parameter space. Finally, our experimental measurements in the microwave regime with a large array of high-refractive-index disks confirm the theoretical predictions. Our results reveal a simple mechanism to engineer an ultra-narrow BIC-induced transparency band that could be exploited throughout the electromagnetic spectrum with obvious applications in filtering and sensing.

physics.app-ph↗

arXiv2013

Two-dimensional magnetic interactions in LaFeAsO

Inelastic neutron scattering measurements demonstrate that the magnetic interactions in antiferromagnetic LaFeAsO are two-dimensional. Spin wave velocities within the Fe layer and the magnitude of the spin gap are similar to the \textit{A}Fe$_2$As$_2$ based materials. However, the ratio of interlayer and intralayer exchange is found to be less than $\sim 10^{-4}$ in LaFeAsO, very similar to the cuprates, and $\sim$ 100 times smaller than that found in \textit{A}Fe$_2$As$_2$ compounds. The results suggest that the effective dimensionality of the magnetic system is highly variable in the parent compounds of the iron arsenides and weak 3-D interactions may limit the maximum attainable superconducting $T_{c}$.

cond-mat.supr-con↗

arXiv1998

Chiral Disorder in QCD

Using the Gell-Mann-Oakes-Renner (GOR) relation and semi-classical arguments, we show that the bulk quark spectrum in QCD exhibits a variety of regimes including the ergodic one described by random matrix theory. We analyze the quark spectral form-factor in the diffusive and ballistic regime. We suggest that a class of chiral transitions in QCD is possibly of the metal-insulator type, with a universal spectral statistics at the mobility edge.

hep-ph↗