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Register a new userChiral transport of pseudo-spinors induced by synthetic gravitational field in photonic Weyl metamaterials
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Weyl particles exhibit chiral transport property under external curved space-time geometry. This effect is called chiral gravitational effect, which plays an important role in quantum field theory. However, the absence of real Weyl particles in nature hinders the observation of such interesting phenomena. In this paper, we show that chiral gravitational effect can be manifested in Weyl metamaterials with spatially controlled nonlocality. This inhomogeneous modulation results in a spatially dependent group velocity in the Weyl cone dispersion, which is equivalent to introducing a curved background space-time (or gravitational field) for Weyl pseudo-spinors. The synthetic gravitational field leads to the quantization of energy levels, including chiral zeroth order energy modes (or simply chiral zero modes) that determine the chiral transport property of pseudo-spinors. The inhomogeneous Weyl metamaterial provides an experimentally realizable platform for investigating the interaction between Weyl particles and gravitational field, allowing for observation of chiral gravitational effect in table-top experiments.
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Topological valley photonics has emerged as a new frontier in photonics with many promising applications. Previous valley boundary transport relies on kink states at internal boundaries between two topologically distinct domains. However, recent studies have revealed a novel class of topological chiral edge states (CESs) at external boundaries of valley materials, which have remained elusive in photonics. Here, we propose and experimentally demonstrate the topological CESs in valley photonic metamaterials (VPMMs) by accurately tuning on-site edge potentials. Moreover, the VPMMs work at deep-subwavelength scales. Thus, the supported CESs are highly confined and self-guiding without relying on a cladding layer to prevent leakage radiation. Via direct near-field measurements, we observe the bulk bandgap, the edge dispersions, and the robust edge transport passing through sharp corners, which are hallmarks of the CESs. Our work paves a way to explore novel topological edge states in valley photonics and sheds light on robust and miniaturized photonic devices.
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