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The huge dielectric constant of ferroelectric nematic liquid crystals (FNLCs) seems to bring about a difficulty of molecular alignment control in exchange for a potential device application. To obtain a satisfactory level of uniform molecular alignment, it is essential to understand how the molecules near the alignment surface are anchored. In this study, bulk molecular alignment with an anti-parallel rubbing manner, which has not yet been investigated extensively, is explained using a conventional torque balance model introducing a polar anchoring function, and it is shown that the disappearance of the bulk twist alignment with decreasing cell thickness can be explained self-consistently. To validate this estimation for a room-temperature FNLC substance, the Brewster angle reflection method was attempted to confirm the surface director’s deviation from the rubbing direction caused by the polar surface anchoring.

Magnetotelluric (MT) and wide-angle seismic reflection/refraction surveys play a fundamental role in understanding the crustal rheology and lithospheric structure of the Earth. In recent years, the integration of the two methods in order to improve the robustness of the inversion has started to gain attention. We present a new approach for joint 3-D inversion of MT and wide-angle seismic reflection/refraction data to accurately determine crustal structures and Moho depth. Based on H-κ stacking of teleseismic receiver functions (RFs), we estimate an initial reference Moho. This is used as input for the subsequent MT/seismic joint inversion, where the Moho interface is updated and crustal structures are added to the model. During the joint inversion process, structural similarity is facilitated through the cross-gradient constraint. Synthetic model tests show an improvement of the inversion results over separate inversions. In particular, the tests based on two geologically realistic models demonstrate that the crustal structure and even the trade-off between velocity and Moho interface can be sufficiently resolved by combined MT and seismic datasets when using the estimates from analysis of RFs. These results show that the new method can provide useful constraints on crustal structures including their geophysical properties and discontinuities.

To investigate the geodynamic processes of Mesozoic large-scale mineralization in South China, we deployed a 350-km-long, wide-angle seismic reflection/refraction sounding profile between Yingshan in Hubei and Changshan in Zhejiang. This profile traverses the Cu-Au metallogenic belt in the middle and lower reaches of the Yangtze River (YMB), the Jiangnan W-polymetal metallogenic belt (JNMB), and the Qinhang Cu-polymetal metallogenic belt (QHMB). Our imaging results reveal various interesting velocity features along the profile. (1) The velocity structure is characterized by vertical layering and horizontal blocking; (2) the YMB is marked by high velocity and high V p / V s ratios in general with a significantly uplifted Moho interface and a thin crust of ∼31 km, and the lower crust contains high-velocity anomalies and has the characteristics of a crust-mantle transition zone; (3) the JNMB is bounded by the Jiangnan fault and Jingdezhen-Huangshan fault and has low-velocity anomalies and low V p / V s ratios; and (4) the QHMB is characterized by high-velocity anomalies and high V p / V s ratios. The high-velocity anomalies in the YMB and QHMB represent relatively Cu-Au-rich mafic juvenile lower crust. The formation of this kind of crust is considered to be related to mantle-derived magma underplating or residues of Neoproterozoic oceanic crustal materials, and it also provided sources for large-scale Cu-Au mineralization in the Mesozoic. The JNMB has features similar to those of ancient crusts enriched in W-Sn, the partial melting of which played a leading role in the formation of the superlarge W deposits in this belt. Considering these results and other regional geological data, we propose that a large-scale oblique upwelling of the asthenosphere along the collisional belt of the Yangtze and Cathaysia blocks during the Mesozoic was the deep driving mechanism for the explosive mineralization of Cu, Au, and W in northeastern South China. The boundaries of the blocks or terrains and discontinuities of the lithosphere were the main channels for deep heat and magmas and therefore controlled the spatial distribution of the metallogenic belt.

Butterfly coloration originates from the finely structured scales grown on the underlying wing cuticle. Most researchers who study butterfly scales are focused on the static optic properties of cover scales, with few works referring to dynamic optical properties of the scales. Here, the dynamic coloration effect of the multiple scales was studied based on the measurements of varying-angle reflection and the characterization of scale flexibility in two species of Lycaenid, Plebejus argyrognomon with violet wings and Polyommatus erotides with blue wings. We explored the angle-dependent color changeability and the color-mediating efficiency of wing scales. It was found that the three main kinds of flexible scales (cover, ground and androconia scales) were asynchronously bent during wing rotation, which caused the discoloration effect. The three layers of composite scales broaden the light signal when compared to the single scale, which may be of great significance to the recognition of insects. Specifically, the androconia scales were shown to strongly contribute to the overall wing coloration. The cover scale coloration was ascribed to the coherence scattering resulted from the short-range order at intermediate spatial frequencies from the 2D Fourier power spectra. Our findings are expected to deepen the understanding of the complex characteristics of biological coloration and to provide new inspirations for the fabrication of biomimetic flexible discoloration materials.

Strongly bound excitons in atomically thin transition metal dichalcogenides offer many opportunities to reveal the underlying physics of basic quasiparticles and many-body effects in the two-dimensional (2D) limit. Comprehensive reflection investigation on band-edge exciton transitions is essential to exploring wealthy light-matter interactions in the emerging 2D semiconductors, whereas angle-resolved reflection (ARR) characteristics of intralayer and interlayer excitons in 2D MoS 2 layers remain unclear. Herein, we report ARR spectroscopic features of A, B, and interlayer excitons in monolayer (ML) and bilayer (BL) MoS 2 on three kinds of photonic substrates, involving distinct exciton-photon interactions. In a BL MoS 2 on a protected silver mirror, the interlayer exciton with one-third amplitude of A exciton appears at 0.05 eV above the A exciton energy, exhibiting an angle-insensitive energy dispersion. When ML and BL MoS 2 lie on a SiO 2 -covered silicon, the broad trapped-photon mode weakly couples with the reflection bands of A and B excitons by the Fano resonance effect, causing the asymmetric lineshapes and the redshifted energies. After transferring MoS 2 layers onto a one-dimensional photonic crystal, two high-lying branches of B-exciton polaritons are formed by the interactions between B excitons and Bragg photons, beyond the weak-coupling regime. This work provides ARR spectral benchmarks of A, B, and interlayer excitons in ML and BL MoS 2 , gaining insights into the interpretation of light-matter interactions in 2D semiconductors and the design of their devices for practical photonic applications.

The eastern North American rifted margin is a passive tectonic margin that has experienced Paleozoic ocean closure and Mesozoic continent rifting. To understand evolution of this continental margin, we modeled the two-dimensional P-wave and S-wave seismic velocity structure of the crust with a seismic wide-angle reflection/refraction profile located in North Carolina and Virginia. There is a seismic low-velocity zone (LVZ) at 10–12 km depth beneath the western segment of the profile. We infer the LVZ to be the base of a Paleozoic metasedimentary succession beneath the eastern Piedmont and westernmost coastal plain. The P-wave velocity and Poisson’s ratio suggest a felsic composition for the upper and middle crust beneath the seismic profile, and an intermediate composition for the lower crust. Overall, the measured crustal velocities and the lateral homogeneity of the crust, especially the middle and lower crust, indicate that Laurentian middle and lower crust extends beneath the entire coastal plain. The lack of a basal crustal layer with a high seismic velocity indicates that no magmatic intrusions have underplated the eastern Piedmont and coastal plain. The comparison with South China Sea, which is a wide rift, and Kenya Rift, which is a narrow rift, indicates that eastern North American margin has the character of a narrow rift. We infer that narrow rifts and wide rifts may have similar crustal compositions, but show strong differences in crustal thickness and the distribution of basal crustal mafic intrusion. These differences may be related to differences in extensional rate during rifting.

In this paper, we propose a new metasurface that is able to reflect a known incoming electromagnetic wave into an arbitrary direction, with perfect power efficiency. This seemingly simple task, which we hereafter call perfect anomalous reflection, is actually highly nontrivial because of the differing wave impedances and complex interference between the incident and reflected waves. Heretofore, proposed metasurfaces that achieve perfect anomalous reflection require complicated, deeply subwavelength and/or multilayer element structures, which allow them to couple to and from leaky and/or evanescent waves. In contrast, we demonstrate that using a bipartite Huygens’ metasurface (BHM)—a passive and lossless metasurface with only two cells per period—perfect anomalous reflection can be achieved over a wide angular and frequency range. Through simulations and experiments at 24 GHz, we show that a properly designed BHM can anomalously reflect an incident electromagnetic wave fromθi=50°toθr=−22.5°, with perfect power efficiency to within experimental precision.

The dynamic control of electromagnetic waves is a persistent pursuit in modern industrial development. The state-of-the-art dynamic devices suffer from limitations such as narrow bandwidth, limited modulation range, and expensive features. To address these issues, we fuse origami techniques with metamaterial design to achieve ultra-wideband and large-depth reflection modulation. Through a folding process, our proposed metamaterial achieves over 10-dB modulation depth over 4.96 – 38.8 GHz, with a fractional bandwidth of 155% and tolerance to incident angles and polarizations. Its ultra-wideband and large-depth reflection modulation performance is verified through experiments and analyzed through multipole decomposition theory. To enhance its practical applicability, transparent conductive films are introduced to the metamaterial, achieving high optical transparency (>87%) from visible to near-infrared light while maintaining cost-effectiveness. Benefiting from lightweight, foldability, and low-cost properties, our design shows promise for extensive satellite communication and optical window mobile communication management. The researchers fuse metamaterials and origami technical to achieve ultra-wideband and large-depth reflection modulation. Flexible electronics amplify its lightweight, transparency, and cost-effectiveness, making it ideal for satellite communications.

Controlling and channeling light emissions from unpolarized quantum dots into specific directions with chiral polarization remains a key challenge in modern photonics. Stacked metasurface designs offer a potential compact solution for chirality and directionality engineering. However, experimental observations of directional chiral radiation from resonant metasurfaces with quantum emitters remain obscure. In this paper, we present experimental observations of unidirectional chiral emission from a twisted bi-layer metasurface via multi-dimensional control, including twist angle, interlayer distance, and lateral displacement between the top and bottom layers, as enabled by doublet alignment lithography (DAL). First, maintaining alignment, the metasurface demonstrates a resonant intrinsic optical chirality with near-unity circular dichroism of 0.94 and reflectance difference of 74%, where a high circular dichroism greater than 0.9 persists across a wide range of angles from −11 to 11 degrees. Second, engineered lateral displacement induces a unidirectional chiral resonance, resulting in unidirectional chiral emission from the quantum dots deposited onto the metasurface. Our bi-layer metasurfaces offer a universal compact platform for efficient radiation manipulation over a wide angular range, promising potential applications in miniaturized lasers, grating couplers, and chiral nanoantennas. Simultaneous control of the direction and polarization of quantum emission using photonic nanostructures is a long-standing challenge in photonics. Here, the authors experimentally demonstrate unidirectional chiral emission from a twisted bilayer metasurface with multi-dimensional control.

Gas permeation through nanoscale pores is ubiquitous in nature and has an important role in many technologies 1 , 2 . Because the pore size is typically smaller than the mean free path of gas molecules, the flow of the gas molecules is conventionally described by Knudsen theory, which assumes diffuse reflection (random-angle scattering) at confining walls 3 – 7 . This assumption holds surprisingly well in experiments, with only a few cases of partially specular (mirror-like) reflection known 5 , 8 – 11 . Here we report gas transport through ångström-scale channels with atomically flat walls 12 , 13 and show that surface scattering can be either diffuse or specular, depending on the fine details of the atomic landscape of the surface, and that quantum effects contribute to the specularity at room temperature. The channels, made from graphene or boron nitride, allow helium gas flow that is orders of magnitude faster than expected from theory. This is explained by specular surface scattering, which leads to ballistic transport and frictionless gas flow. Similar channels, but with molybdenum disulfide walls, exhibit much slower permeation that remains well described by Knudsen diffusion. We attribute the difference to the larger atomic corrugations at molybdenum disulfide surfaces, which are similar in height to the size of the atoms being transported and their de Broglie wavelength. The importance of this matter-wave contribution is corroborated by the observation of a reversed isotope effect, whereby the mass flow of hydrogen is notably higher than that of deuterium, in contrast to the relation expected for classical flows. Our results provide insights into the atomistic details of molecular permeation, which previously could be accessed only in simulations 10 , 14 , and demonstrate the possibility of studying gas transport under controlled confinement comparable in size to the quantum-mechanical size of atoms. Specular scattering of atoms of helium gas flowing through atomically flat, two-dimensional channels results in frictionless gas flow, which is much faster than expected assuming purely diffusive scattering.