We report that equidistant 1D arrays of thin-film lithium niobate nano-waveguides generically support topological edge states. Unlike conventional coupled-waveguide topological systems, the topological properties of these arrays are dictated by the interplay between intra- and inter-modal couplings of two families of guided modes with different parities. Exploiting two modes within the same waveguide to design a topological invariant allows us to decrease the system size by a factor of two and substantially simplify the structure. We present two example geometries where topological edge states of different types (based on either quasi-TE or quasi-TM modes) can be observed within a wide range of wavelengths and array spacings.
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http://dx.doi.org/10.1364/OL.485415 | DOI Listing |
Nature
January 2025
Department of Chemistry, National University of Singapore, Singapore, Singapore.
Topological design of π electrons in zigzag-edged graphene nanoribbons (ZGNRs) leads to a wealth of magnetic quantum phenomena and exotic quantum phases. Symmetric ZGNRs typically show antiferromagnetically coupled spin-ordered edge states. Eliminating cross-edge magnetic coupling in ZGNRs not only enables the realization of a class of ferromagnetic quantum spin chains, enabling the exploration of quantum spin physics and entanglement of multiple qubits in the one-dimensional limit, but also establishes a long-sought-after carbon-based ferromagnetic transport channel, pivotal for ultimate scaling of GNR-based quantum electronics.
View Article and Find Full Text PDFComput Biol Med
January 2025
Department of Mathematics, COMSATS University Islamabad, Vehari Campus, 61100, Vehari, Pakistan. Electronic address:
Topological indices, derived from molecular graphs, provide valuable numerical descriptors for the comprehensive analysis of pharmaceuticals. These indices are pivotal in the physicochemical characterization and predictive assessment of various drugs. In this study, we calculate several degree-based topological indices for a range of migraine treatment medications, including aspirin, caffeine, eletriptan, ergotamine, sumatriptan, rizatriptan, verapamil, diclofenac, frovatriptan, and droperidol.
View Article and Find Full Text PDFSci Rep
January 2025
College of Computer and Information Engineering, Nanjing Tech University, Nanjing, 211800, China.
Graph data is essential for modeling complex relationships among entities. Graph Neural Networks (GNNs) have demonstrated effectiveness in processing low-order undirected graph data; however, in complex directed graphs, relationships between nodes extend beyond first-order connections and encompass higher-order relationships. Additionally, the asymmetry introduced by edge directionality further complicates node interactions, presenting greater challenges for extracting node information.
View Article and Find Full Text PDFNano Lett
January 2025
Institute of Experimental and Applied Physics, Kiel University, Leibnizstr. 11-19, Kiel 24098, Germany.
Topological plasmonics combines principles of topology and plasmonics to provide new methods for controlling light, analogous to topological edge states in photonics. However, designing such topological states remains challenging due to the complexity of the high-dimensional design space. We present a novel method that uses supervised, physics-informed deep learning and surrogate modeling to design topological devices for desired wavelengths.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
School of Physics, Beihang University, Haidian District, Beijing 100191, China.
Massive Dirac fermions, which are essential for realizing novel topological phenomena, are expected to be generated from massless Dirac fermions by breaking the related symmetry, such as time-reversal symmetry in topological insulators or crystal symmetry in topological crystalline insulators. Here, we report scanning tunneling microscopy and angle-resolved photoemission spectroscopy studies of α-Bi_{4}I_{4}, which reveals the realization of massive Dirac fermions in the (100) surface states without breaking the time-reversal symmetry. Combined with first-principles calculations, our experimental results indicate that the spontaneous symmetry breaking engenders two nondegenerate edge states at the opposite sides of monolayer Bi_{4}I_{4} after the structural phase transition, imparting mass to the Dirac fermions after taking the interlayer coupling into account.
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