Quantum simulation of particle pair creation near the event horizon

Geometrical Theory of Electromagnetic Nonreciprocity

Recent advances in electromagnetic nonreciprocity raise the question of how to engineer the nonreciprocal electromagnetic response with geometrical approaches. In this Letter, we examine this problem by introducing generalized electromagnetic continua consisting structured points, which carry extra degrees of freedom over coordinate transformation. We show that general nonreciprocal media have a unique time-varying Riemannian metric structure with local spinning components. It is demonstrated that the nonreciprocity can be alternatively identified as the torsion tensor of a Riemann-Cartan space, which could provide analytic expressions for the magneto-optical effect and the axionic magnetoelectric coupling. Our theory not only gives a deeper insight into the fundamental understanding of electromagnetic nonreciprocity but also provides a practical principle to geometrically design nonreciprocal devices through frame transformation.

Black-hole-inspired thermal trapping with graded heat-conduction metadevices

The curved space-time produced by black holes leads to the intriguing trapping effect. So far, metadevices have enabled analogous black holes to trap light or sound in laboratory spacetime. However, trapping heat in a conductive environment is still challenging because diffusive behaviors are directionless. Inspired by black holes, we construct graded heat-conduction metadevices to achieve thermal trapping, resorting to the imitated advection produced by graded thermal conductivities rather than the trivial solution of using insulation materials to confine thermal diffusion. We experimentally demonstrate thermal trapping for guiding hot spots to diffuse towards the center. Graded heat-conduction metadevices have advantages in energy-efficient thermal regulation because the imitated advection has a similar temperature field effect to the realistic advection that is usually driven by external energy sources. These results also provide an insight into correlating transformation thermotics with other disciplines, such as cosmology, for emerging heat control schemes.

Anomalous π modes by Floquet engineering in optical lattices with long-range coupling

Photonic Floquet topological insulators provide a powerful tool to manipulate the optical fields, which have been extensively studied with only nearest-neighbor coupling. Here, we demonstrate that nontrivial Floquet topological phase and photonic π modes are brought from long-range coupling in a one-dimensional periodically driven optical lattice. Interestingly, the long-range coupling is found to give rise to new Floquet π modes that do not exist in the traditional Floquet lattices. We interpret the underlying physics by analyzing the replica bands, which shows quasienergies band crossing and reopening of new nontrivial π gaps due to the long-range coupling. Our results provide a new route in manipulating optical topological modes by Floquet engineering with long-range coupling.

Bound vortex light in an emulated topological defect in photonic lattices

Topology have prevailed in a variety of branches of physics. And topological defects in cosmology are speculated akin to dislocation or disclination in solids or liquid crystals. With the development of classical and quantum simulation, such speculative topological defects are well-emulated in a variety of condensed matter systems. Especially, the underlying theoretical foundations can be extensively applied to realize novel optical applications. Here, with the aid of transformation optics, we experimentally demonstrated bound vortex light on optical chips by simulating gauge fields of topological linear defects in cosmology through position-dependent coupling coefficients in a deformed photonic graphene. Furthermore, these types of photonic lattices inspired by topological linear defects can simultaneously generate and transport optical vortices, and even can control the orbital angular momentum of photons on integrated optical chips.

Transformation Metamaterials

Based on the form-invariance of Maxwell's equations under coordinate transformations, mathematically smooth deformation of space can be physically equivalent to inhomogeneous and anisotropic electromagnetic (EM) medium (called a transformation medium). It provides a geometric recipe to control EM waves at will. A series of examples of achieving transformation media by artificially structured units from conventional materials is summarized here. Such concepts are firstly implemented for EM waves, and then extended to other wave dynamics, such as elastic waves, acoustic waves, surface water waves, and even stationary fields. These shall be cataloged as transformation metamaterials. In addition, it might be conceptually attractive and practically useful to control diverse waves for multi-physics designs.