Direct observation of photonic Landau levels and helical edge states in strained honeycomb lattices

We report the realization of a synthetic magnetic field for photons and polaritons in a honeycomb lattice of coupled semiconductor micropillars.A strong synthetic field is induced in both the s and p orbital bands by engineering a uniaxial hopping gradient in the lattice,giving rise to the formation of Landau levels at the Dirac points.We provide direct evidence of the sublattice symmetry breaking of the lowest-order Landau level wavefunction,a distinctive feature of synthetic magnetic fields.Our realization implements helical edge states in the gap between n=0 and n=±1 Landau levels,experimentally demonstrating a novel way of engineering propagating edge states in photonic lattices.In light of recent advances in the enhancement of polariton–polariton nonlinearities,the Landau levels reported here are promising for the study of the interplay between pseudomagnetism and interactions in a photonic system.

Erratum to:Influence of metal support in-plane symmetry on the corrugation of hexagonal boron nitride and graphene monolayers

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Plasmon-induced dual-wavelength operation in a Yb^(3+) laser

Expanding the functionalities of plasmon-assisted lasers is essential for emergent applications in nanoscience and nanotechnology.Here,we report on a novel ability of plasmonic structures to induce dual-wavelength lasing in the near-infrared region in a Yb^(3+) solid-state laser.By means of the effects of disordered plasmonic networks deposited on the surface of a Yb^(3+)-doped nonlinear RTP crystal,room-temperature dual-wavelength lasing,with a frequency difference between the lines in the THz range,is realized.The dual-wavelength laser is produced by the simultaneous activation of two lasing channels,namely,an electronic-and a phonon-terminated laser transition.The latter is enabled by the out-of-plane field components that are generated by the plasmonic structures,which excite specific Raman modes.Additionally,multiline radiation at three different wavelengths is demonstrated in the visible spectral region via two self-frequency conversion processes,which occur in the vicinities of the plasmonic structures.The results demonstrate the potential of plasmonic nanostructures for inducing drastic modifications in the operational mode of a solid-state laser and hold promise for applications in a variety of fields,including multiplexing,precise spectroscopies,and THz radiation generation via a simple and cost-effective procedure.

Water-induced hydrogenation of graphene/metal interfaces at room temperature:Insights on water intercalation and identification of sites for water splitting

Though it is well recognized that the space between graphene cover and the metal substrate canact as a two-dimensional(2D)nanoreactor,several issues are still unresolved,including the role of the metal substrate,the mechanisms ruling water intercalation and the identification ofsites at which water is decomposed.Here,we solve these issues by means of density functional theory and high-resolution electron energyloss spectroscopy experiments carried out on graphene grown on(111)-oriented Cu foils.Specifically,we observe decomposition of H2O atroom temperature with only H atoms forming bonds with graphene and with buried OH groups underneath the graphene cover.Ourtheoretical model discloses physicochemical mechanisms ruling the migration and decomposition of water on graphene/Cu.We discover thatthe edge of graphene can be easily saturated by H through decomposition of H2O,which allows H2O to migrate in the subsurface region from thedecoupled edge,where H2O decomposes at room temperature.Hydrogen atoms produced by the decomposition of H2O initially form a chemicalbond with graphene for the lower energy barrier compared with other routes.These findings are essential to exploit graphene/Cu interfaces incatalysis and in energy-related applications.