Bound states in the continuum (BICs) have attracted much attention in Nanophotonics for their (formally) infinite Q factors, quasi‐BICs (qBICs) being the symmetry‐broken version allowing for in‐ and out‐coupling at the expense of finite (but large) Q factors. Here, it is demonstrated that dark and asymmetric qBICs arise in the optical domain in Si tilted nanodisk metasurfaces, due to the spectral overlap of in‐plane and out‐of‐plane dipolar resonances in these meta‐atoms, similar to so called Brewster qBICs in the microwave regime for single‐magnetic‐resonance, tilted microdisks, arising at the tilt angle. Using a coupled dipole model, it is shown that optical dark qBICs occur for tilted nanodisks at modified Brewster angles that can differ significantly from the nanodisk tilt angles, , due to the hybridization of in‐plane and out‐of‐plane dipolar resonances. If light is incident at , qBIC excitation is forbidden and the metasurface is transparent; counterintuitively, for , the qBIC is indeed excited but the metasurface remains also fully transparent, so that such qBIC excitation is cloaked. Numerical calculations confirm the asymmetric character of these qBICs, demonstrating that the cloaked qBIC largely enhances near‐fields and emerges in the extinction only when absorptive losses are present in the nanodisks. Finally, a practical metasurface design is proposed, amenable to fabrication, supporting cloaked qBICs. The rich phenomena associated with such cloaked qBICs make them highly suitable for tuning or switching nano‐optical devices (between on/off qBIC states with negligible reflection), offering promising applications for enhanced light–matter interactions at the nanoscale.
Passive radiative cooling, which uses the cold sink of outer space for sub‐ambient cooling, offers a sustainable alternative to energy‐intensive conventional cooling methods. This study investigates the impact of transversal channel distances within three dimensional‐ 3D‐ anodic aluminum oxide (AAO) dielectric and inorganic nanostructures on their morphology, emissivity, and passive radiative cooling performance. 3D‐AAO nanostructures with varying alumina thicknesses and transverse channel spacings are fabricated. 3D‐AAO metamaterials on Aluminium ‐ Al‐ bulk with larger transverse channel distances exhibit high solar reflectance and high mid‐IR emissivity, since they act as Bragg reflectors. Their porosity is significantly higher than the more common 1D‐AAO due to the periodically ordered transverse channels. Cooling power density calculations showed that greater transverse channel distances improve daytime cooling performance. Outdoor characterization under direct sunlight confirmed these findings, with a 3D‐AAO nanostructure on Al bulk achieving a maximum temperature reduction of 10.2 °C. This research establishes the critical role of transverse nanochannels in tailoring the radiative cooling properties of durable, inorganic, all‐dielectric 3D‐AAO nanostructures and highlights their potential for multiple applications, including energy‐efficient building cooling.
Selecting a set of reactants to accurately design a new low dimensional hybrid perovskite could greatly accelerate the discovery of materials with great potential in photovoltaics, or solid-state lighting. However, this design is challenging as most hybrid metal halides are not perovskites and no feature is clearly associated to the structural characteristics of the inorganic metal halide network. This work first demonstrates that the organic molecules are key parameters to determine the structure type of the inorganic network (i.e., perovskite versus non-perovskite). Then, machine learning (ML) algorithms are used to identify the key features of the organic cations leading to the perovskite structure type. Using a large dataset of hybrid metal halides, this work extracts the organic molecules of all hybrid lead halide compounds, calculates 2756 molecular descriptors and fingerprints for each of these molecules, and are able to predict through ML techniques if a specific organic amine will lead to the perovskite type with an accuracy up to 88.65%. Descriptors related to hydrogen bonding are identified as important features. Thus, a simple but reliable design principle could be demonstrated: the presence of primary ammonium cation is the primary condition to prepare hybrid lead halide perovskites regardless of their dimensionalities.
A search for the nonresonant production of Higgs boson pairs in the HH→bb¯τ+τ− channel is performed using 140 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The analysis strategy is optimized to probe anomalous values of the Higgs boson self-coupling modifier κλ and of the quartic HHVV (V=W,Z) coupling modifier κ2V. No significant excess above the expected background from Standard Model processes is observed. An observed (expected) upper limit μHH<5.9(3.3) is set at 95% confidence-level on the Higgs boson pair production cross section normalized to its Standard Model prediction. The coupling modifiers are constrained to an observed (expected) 95% confidence interval of −3.1<κλ<9.0 (−2.5<κλ<9.3) and −0.5<κ2V<2.7 (−0.2<κ2V<2.4), assuming all other Higgs boson couplings are fixed to the Standard Model prediction. The results are also interpreted in the context of effective field theories via constraints on anomalous Higgs boson couplings and Higgs boson pair production cross sections assuming different kinematic benchmark scenarios. © 2024 CERN, for the ATLAS Collaboration 2024 CERN
Measurements of the substructure of top-quark jets are presented, using 140 fb−1 of 13 TeV pp collision data recorded with the ATLAS detector at the LHC. Top-quark jets reconstructed with the anti-kt algorithm with a radius parameter R=1.0 are selected in top-quark pair (tt¯) events where one top quark decays semileptonically and the other hadronically, or where both top quarks decay hadronically. The top-quark jets are required to have transverse momentum pT>350 GeV, yielding large samples of data events with jet pT values between 350 and 600 GeV. One- and two-dimensional differential cross sections for eight substructure variables, defined using only the charged components of the jets, are measured in a particle-level phase space by correcting for the smearing and acceptance effects induced by the detector. The differential cross sections are compared with the predictions of several Monte Carlo simulations in which top-quark pair-production quantum chromodynamic matrix-element calculations at next-to-leading-order precision in the strong coupling constant αS are passed to leading-order parton shower and hadronization generators. The Monte Carlo predictions for measures of the broadness, and also the two-body structure, of the top-quark jets are found to be in good agreement with the measurements, while variables sensitive to the three-body structure of the top-quark jets exhibit some tension with the measured distributions. © 2024 CERN, for the ATLAS Collaboration 2024 CERN
