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Topological wave phenomena in photonic time quasicrystals

Physical Review B 2025年第12期111卷 125421-125421页

作者： Xiang Ni Shixiong Yin Huanan Li Andrea Alù School of Physics Central South University Changsha 410083 China Photonics Initiative Advanced Science Research Center City University of New York New York New York 10031 USA Department of Electrical Engineering City College of The City University of New York New York 10031 USA MOE Key Laboratory of Weak-Light Nonlinear Photonics School of Physics Nankai University Tianjin 300071 China Physics Program Graduate Center City University of New York New York New York 10016 USA

Time interfaces consist of abrupt and spatially uniform changes in the optical properties of a medium. Their periodic occurrence forms photonic time crystals, which offer opportunities to tailor classical and quantum light-matter interactions. Here we explore one-dimensional photonic time quasicrystals, formed when time interfaces occur in a quasiperiodic fashion featuring long-range order. We unveil the emergence of topological phases and Hofstadter butterfly spectra in these systems, and demonstrate that their temporal response emulates the localization of topological edge states, enabling the temporal analog of topological Thouless pumping. Our findings open avenues for topological photonics leveraging time as a synthetic dimension, with functionalities that go beyond their spatial counterparts.

关键词： Quasicrystals

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Observation of Photonic Chiral Flatbands

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Physical Review Letters 2025年第10期134卷 103801-103801页

作者： Minho Choi Andrea Alù Arka Majumdar Department of Electrical and Computer Engineering University of Washington Seattle Washington 98195 USA Photonics Initiative Advanced Science Research Center City University of New York New York New York 10031 USA and Physics Program Graduate Center City University of New York New York New York 10031 USA Department of Electrical and Computer Engineering University of Washington Seattle Washington 98195 USA and Department of Physics University of Washington Seattle Washington 98195 USA

Distinct selectivity to the spin angular momenta of photons has garnered significant attention in recent years, for its relevance in basic science and for imaging and sensing applications. While nonlocal metasurfaces with strong chiral responses to the incident light have been reported, these responses are typically limited to a narrow range of incident angles. In this study, we demonstrate a nonlocal metasurface that showcases strong chirality, characterized by circular dichroism (∼0.6), over a wide range of incident angles ±5°. Its quality factor, circular dichroism and resonant frequency can be optimized by design. These findings pave the way to further advance the development of valley-selective optical cavities and augmented reality applications.

关键词： Natural frequencies

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Chiral exceptional point enhanced active tuning and non reciprocity in micro-resonators

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光：科学与应用（英文版） 2025年第2期14卷 401-410页

作者： Hwaseob Lee Lorry Chang Ali Kecebas Dun Mao Yahui Xiao Tiantian Li Andrea Alù Sahin K.Özdemir Tingyi Gu Department of Electrical and Computer Engineering University of DelawareNewarkDelaware 19716USA Department of Engineering Science and Mechanics Pennsylvania State UniversityUniversity ParkPA 16802USA Photonics Initiative Advanced Science Research CenterCity University of New YorkNew YorkNY 10031USA Physics Program Graduate CenterCity University of New YorkNew YorkNY 10016USA Department of Engineering Science and Mechanics Pennsylvania State UniversityUniversity ParkPA 16802USA Department of Electrical and Computer Engineering Saint Louis UniversitySaint LouisMO 63103USA

Exceptional points(EPs)have been extensively explored in mechanical,acoustic,plasmonic,and photonic ***,little is known about the role of EPs in tailoring the dynamic tunability of optical devices.A specific type of EPs known as chiral EPs has recently attracted much attention for controlling the flow of light and for building sensors with better responsivity.A recently demonstrated route to chiral EPs via lithographically defined symmetric Mie scatterers on the rim of resonators has not only provided the much-needed mechanical stability for studying chiral EPs,but also helped reduce losses originating from nanofabrication imperfections,facilitating the in-situ study of chiral EPs and their contribution to the dynamics and tunability of ***,we use asymmetric Mie scatterers to break the rotational symmetry of a microresonator,to demonstrate deterministic thermal tuning across a chiral EP,and to demonstrate EP-mediated chiral optical nonlinear response and efficient electro-optic *** results indicate asymmetric electro-optic modulation with up to 17 dB contrast at GHz and CMOS-compatible voltage *** wafer-scale nano-manufacturing of chiral electro-optic modulators and the chiral EP-tailored tunning may facilitate new micro-resonator functionalities in quantum information processing,electromagnetic wave control,and optical interconnects.

关键词： active point micro chiral enhanced exceptional reciprocity resonators tuning

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Reorientation of ferroelectric nematic liquid crystals under out-of-plane electric and magnetic fields

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Journal of Molecular Liquids 2025年 428卷

作者： Máthé, Marcell Tibor Éber, Nándor Buka, Ágnes Nishikawa, Hiroya Araoka, Fumito Jákli, Antal Salamon, Péter Institute for Solid State Physics and Optics HUN-REN Wigner Research Centre for Physics P.O. Box 49 BudapestH-1525 Hungary RIKEN Center for Emergent Matter Science 2-1 Hirosawa Saitama Wako351-0198 Japan Materials Sciences Graduate Program and Advanced Materials and Liquid Crystal Institute Kent State University KentOH44242 United States Department of Physics Kent State University KentOH44242 United States

The recently discovered ferroelectric nematic liquid crystals combine fluidic properties and spontaneous electric polarization with an externally controllable molecular arrangement. The huge spontaneous polarization and large apparent permittivity along with the soft nature suggest an extreme sensitivity and reconfigurability by external electric fields, promising new perspectives in applications. In this paper, we show that it is possible to induce a thresholdless reorientation of the molecular arrangement by an electric field normal to the initial orientation and the bounding surfaces. Continuum theoretical description involving orientational elasticity, ferro-electrostatics, and an external electric field is presented, where the effect of magnetic fields applied in different directions is also discussed. Our simulations and experiments show thresholdless reorientation in contrast to the Fredericks transition observed in conventional nematic liquid crystals, while the ordering remains to be monodomain except at the boundaries. The experiments also show the importance of ionic charges present in the material. © 2025

关键词： Ferroelectricity

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Emulating complex synapses using interlinked proton conductors

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Physical Review Applied 2025年第1期23卷 014027-014027页

作者： Lifu Zhang Ji-An Li Yang Hu Jie Jiang Rongjie Lai Marcus K. Benna Jian Shi Department of Materials Science and Engineering Rensselaer Polytechnic Institute Troy New York 12180 USA Neurosciences Graduate Program University of California San Diego La Jolla California 92093 USA Department of Mathematics Purdue University West Lafayette Indiana 47907 USA Department of Neurobiology School of Biological Sciences University of California at San Diego La Jolla California 92093 USA Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy New York 12180 USA

In terms of energy efficiency and computational speed, neuromorphic electronics based on nonvolatile memory devices are expected to be one of most promising hardware candidates for future artificial intelligence (AI). However, catastrophic forgetting, networks rapidly overwriting previously learned weights when learning new tasks, remains a pivotal obstacle in either digital or analog AI chips for unleashing the true power of brainlike computing. To address catastrophic forgetting in the context of online memory storage, a complex synapse model (the Benna-Fusi model) was proposed recently [M. K. Benna and S. Fusi, Nat. Neurosci. 19, 1697 (2016)], the synaptic weight and internal variables of which evolve following diffusion dynamics. In this work, by designing a proton transistor with a series of charge-diffusion-controlled storage components, we have experimentally realized the Benna-Fusi artificial complex synapse. Memory consolidation from coupled storage components is revealed by both numerical simulations and experimental observations. Different memory timescales for the complex synapse are engineered by the diffusion length of charge carriers and the capacity and number of coupled storage components. The advantages of the demonstrated complex synapse for both memory capacity and memory consolidation are revealed by neural network simulations of face-familiarity detection. Our experimental realization of the complex synapse suggests a promising approach to enhance memory capacity and to enable continual learning.

关键词： Nonvolatile storage

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Dynamical evolution of critical fluctuations with second-order baryon diffusion coupled to chiral condensate

arXiv

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arXiv 2025年

作者： Sakai, Azumi Murase, Koichi Fujii, Hirotsugu Hirano, Tetsufumi Physics Program Graduate School of Advanced Science and Engineering Hiroshima University Hiroshima Higashi-Hiroshima739-8526 Japan Department of Physics Sophia University Chiyoda Tokyo102-8554 Japan Department of Physics Tokyo Metropolitan University Hachioji Tokyo192-0397 Japan Yukawa Institute for Theoretical Physics Kyoto University Sakyo Kyoto606-8502 Japan International Politics and Economics Nishogakusha University Chiyoda Tokyo102-8336 Japan Institute of Physics Unviversity of Tokyo Meguro Tokyo153-8902 Japan

We develop a dynamical model to describe critical fluctuations in heavy-ion collisions, incorporating the baryon diffusion current and chiral condensate as dynamical degrees of freedom, to address their nontrivial scale separation. The model couples fluctuations of the chiral condensate σ with baryon density fluctuations n and the diffusion current ν based on a second-order diffusion equation with a finite relaxation time of the baryon diffusion τR. We analyze the spacetime evolution and these correlation functions of the fluctuations in one-dimensionally expanding background. We confirm that an appropriate relaxation time τR ensures causality. We show that propagating waves with finite τR split into two modes at the critical temperature due to a rapid change of kinetic coefficients. In the correlation functions, we find that dynamical σ blurs the structure and peak around the critical temperature. With finite τR, the effect of the critical fluctuations persists longer into the later stages of the evolution. These findings suggest importance of dynamical effects of the chiral condensate and baryon diffusion current in identifying critical-point signals in heavy-ion collisions, where the scale separation is nontrivial. Copyright © 2025, The Authors. All rights reserved.

关键词： Heavy ions

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Insights into the role of metal dopant on ammonia decomposition over graphene-supported Ni6, Ni5Pt, and Ni5Rh clusters

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International Journal of Hydrogen Energy 2025年 130卷 168-175页

作者： Yusuf, Alfani Budiantono, Reva Juangsa, Firman Bagja Aziz, Muhammad Budiyanto, Muhammad Arif Saputro, Adhitya Gandaryus Mahyuddin, Muhammad Haris Graduate Program of Engineering Physics Faculty of Industrial Technology Institut Teknologi Bandung Jl. Ganesha 10 Bandung40132 Indonesia PLN Nusantara Power UMRO Jl. Pluit Karang Ayu Barat No. 1 Jakarta14450 Indonesia Thermal Science and Engineering Research Group Faculty of Mechanical and Aerospace Engineering Institut Teknologi Bandung Jl Ganesha 10 Bandung40132 Indonesia Institute of Industrial Science The University of Tokyo 4-6-1 Komaba Meguro-ku Tokyo153-8505 Japan Department of Mechanical Engineering Universitas Indonesia Depok16424 Indonesia Quantum and Nano Technology Research Group Faculty of Industrial Technology Institut Teknologi Bandung Jl. Ganesha 10 Bandung40132 Indonesia Research Center for Nanoscience and Nanotechnology Institut Teknologi Bandung Jl. Ganesha 10 Bandung40132 Indonesia

Ammonia (NH3) is a promising hydrogen (H2) carrier, owing to its high hydrogen content and ease of storage. However, efficient catalytic decomposition of NH3 to H2 remains challenging. This study investigates the catalytic activity of graphene-supported Ni6, Ni5Pt, and Ni5Rh clusters for NH3 decomposition to N2 and H2 using density functional theory (DFT) calculations. The results show that the addition of Pt and Rh dopants weakens the adsorption of intermediates formed during the NH3 dehydrogenation step and slightly increases the activation energies. Interestingly, however, this drawback becomes a key factor in enhancing the activity of the subsequent N–N association and H–H recombination steps, which are critical for the reaction to cycle. Our electronic structure analysis reveals that the decreased activity in the NH3 dehydrogenation step but increased activity in the N2 and H2 formation steps are due to the ligand effect exerted by Pt and Rh. Specifically, since the metal dopants have higher electronegativities than Ni, the number of electrons at the preferred Ni-edge site decreases and eventually weakens the adsorption. Furthermore, the spatially broad nature of the Pt-5d and Rh-4d orbitals delocalizes the cluster's electron distribution, which weakens the 2N and 2H adsorption and thus eases the N2 and H2 formation. This study provides insights into the role of noble metal dopants in optimizing Ni-based catalysts for NH3 decomposition, paving the way for efficient H2 utility technologies. © 2025 Hydrogen Energy Publications LLC

关键词： Dehydrogenation

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Cytocompatible and antibacterial Fe-, Cu- and Zn-substituted calcium hydroxyapatite materials for skin applications

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Ceramics International 2025年第9期51卷 11286-11296页

作者： Lukaviciute, L. Lukowiak, A. Stankeviciute, Z. Junka, A. Mortimer, M. Zarkov, A. Yang, J.-C. Ganceviciene, R. Kareiva, A. Faculty of Chemistry and Geosciences Vilnius University Naugarduko st. 24 Vilnius03225 Lithuania Institute of Low Temperature and Structure Research Polish Academy of Sciences Okolna 2 Wroclaw50422 Poland Department of Pharmaceutical Microbiology and Parasitology Wroclaw Medical University Borowska 211A Wroclaw50556 Poland Laboratory of Environmental Toxicology National Institute of Chemical Physics and Biophysics Akadeemia tee 23 Tallinn12618 Estonia Graduate Institute of Nanomedicine and Medical Engineering International Ph.D. Program in Biomedical Engineering College of Biomedical Engineering Research Center of Biomedical Device Research Center of Digital Oral Science and Technology Taipei Medical University Taiwan Faculty of Medicine Vilnius University M.K. Ciurlionio st. 21 Vilnius03101 Lithuania

Calcium hydroxyapatite (C10(PO4)6(OH)2;CHAp) and metal-substituted samples (Fe:CHAp, Cu:CHAp, and Zn:CHAp) were synthesized using a recently developed method. This method involved the wet precipitation of amorphous calcium phosphate (ACP), followed by solid-state reaction synthesis of α-tricalcium phosphate (α-TCP), and finally hydrothermal synthesis of CHAp. The effect of Fe3+, Cu2+, and Zn2+ substitution on the phase purity and antimicrobial properties of CHAp are summarized in this study. Notably, it highlights the phase purity of CHAp and Zn:CHAp (in the presence of Fe3+ and Cu2+ ions, the α- and β-TCP phases have formed) as well as the antimicrobial activity of Zn:CHAp and Cu:CHAp against Staphylococcus aureus and Candida albicans. The synthesized nanosized CHAp, Fe:CHAp, Cu:CHAp, and Zn:CHAp samples were used as additives in the preparation of skin creams. In vitro biological studies of the resulting skin creams demonstrated their antimicrobial activity against Pseudomonas aeruginosa, and showed a reduction in osteoblasts cells viability of in the range of 20–40 %. The addition of zinc enhances antimicrobial efficacy but reduces biocompatibility, while copper maintains both high antimicrobial activity and biocompatibility, making it more suitable for the development of medical or cosmetic materials. Dermal creams containing CHAp with copper and iron ions also show significant antimicrobial activity while preserving good cell viability. These results highlight the importance of optimizing the balance between antimicrobial effectiveness and biocompatibility in these materials. © 2024

关键词： Biocompatibility

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Freedericskz Transitions in the Nematic and Smectic ZA Phases of DIO

arXiv

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arXiv 2025年

作者： Gleeson, J.T. Sprunt, S.N. Jákli, A. Guragain, P. Twieg, R.J. Department of Physics Kent State University KentOH44242 United States Materials Science Graduate Program and Advanced Materials and Liquid Crystal Institute Kent State University KentOH44242 United States Department of Chemistry and Biochemistry Kent State University KentOH44242 United States

The remarkable material DIO presents fascinating behaviors. It has been extensively studied as one of the first materials exhibiting a ferroelectric nematic phase. However, at higher temperatures it exhibits what has been termed the Smectic ZA: identified as an orientationally ordered, antiferroelectric phase with a density modulation in direction perpendicular to the optic axis. At even higher temperatures, this transitions to an apparently normal nematic phase. We have studied the splay-bend Freedericksz transition in the nematic and SmZA phases of the material DIO. Both the magnetic and electric field transitions were utilized. We observed the transitions by measuring effective birefringence and capacitance as well as with polarizing light microscopy. In both the nematic and the SmZA states the field induced transitions resemble (in numerous aspects) the classical Freedericksz transition. These enable determinations of several fundamental material parameters and also reveal intriguing aspects of the SmZA phase, including the surprising behavior of the elastic constants and the dielectric anisotropy. Detailed comparison with Frank elastic theory of the Freedericksz transition [1] shows that the N phase behaves largely as expected, but the transition in the SmZA phase differs significantly. Two specific examples of this are the onset of striations in the Freedericksz distorted state, and the presence of optical biaxiality. The former may be related to the periodic Freedericksz transition [2] as it coincides with a large increase in the splay elastic constant. The latter has been predicted for the SmZA phase, but not previously observed. [3] © 2025, CC BY.

关键词： Antiferroelectricity

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Twist, splay, and uniform domains in ferroelectric nematic liquid crystals

arXiv

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arXiv 2025年

作者： Lavrentovich, Maxim O. Kumari, Priyanka Lavrentovich, Oleg D. Department of Earth Environment and Physics Worcester State University WorcesterMA01602 United States Department of Physics & Astronomy University of Tennessee KnoxvilleTN37996 United States Advanced Materials and Liquid Crystal Institute Kent State University KentOH44240 United States Materials Science Graduate Program Kent State University KentOH44240 United States Department of Physics Kent State University KentOH44240 United States

The recently-discovered ferroelectric nematic (NF) liquid crystal presents a host of defect phenomena due to its unique polar nature and long-ranged electrostatic interactions. Like the solid state ferroelectrics, the depolarization field in the material favors a spontaneous spatial variation of the polarization P, manifesting in myriad ways including a twist in the bulk and different arrangements of alternating polarization domains. Unlike the solid-state ferroelectrics with a bulk crystalline structure, the configuration of the NF fluids is determined not only by the reduction of depolarization fields but also by the alignment of molecules at interfaces. In this work, we consider an NF confined to a thin cell, pre-patterned with various types of apolar surface anchoring produced by photoalignment. For uniform planar alignment, we find that the sample forms a series of striped domains. For a cell pre-patterned with a radial +1 defect pattern, the NF breaks up into "pie-slice" polarization domains. We calculate the elastic and electrostatic energy balance which determines the observed configurations and demonstrate that the electrostatic interactions tend to decrease the characteristic domain size λ while the elastic and surface anchoring interactions facilitate a larger λ. We also demonstrate that ionic screening mitigates electrostatic interactions, increasing λ and, above some critical concentration, eliminating the domains altogether. Copyright © 2025, The Authors. All rights reserved.

关键词： Depolarization

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