Synthesis, properties, and applications of large-scale two-dimensional materials by polymer-assisted deposition

Two-dimensional(2D) materials have attracted considerable attention because of their novel and tunable electronic,optical, ferromagnetic, and chemical properties. Compared to mechanical exfoliation and chemical vapor deposition, polymer-assisted deposition(PAD) is more suitable for mass production of 2D materials owing to its good reproducibility and reliability. In this review, we summarize the recent development of PAD on syntheses of 2D materials. First, we introduce principles and processing steps of PAD. Second, 2D materials, including graphene, MoS2, and MoS2/glassy-graphene heterostructures, are presented to illustrate the power of PAD and provide readers with the opportunity to assess the method. Last, we discuss the future prospects and challenges in this research field. This review provides a novel technique for preparing 2D layered materials and may inspire new applications of 2D layered materials.

Giant photonic spin Hall effect in momentum space in a structured metamaterial with spatially varying birefringence

The photonic spin Hall effect(SHE)in the reflection and refraction at an interface is very weak because of the weak spin-orbit interaction.Here,we report the observation of a giant photonic SHE in a dielectric-based metamaterial.The metamaterial is structured to create a coordinate-dependent,geometric Pancharatnam–Berry phase that results in an SHE with a spin-dependent splitting in momentum space.It is unlike the SHE that occurs in real space in the reflection and refraction at an interface,which results from the momentum-dependent gradient of the geometric Rytov–Vladimirskii–Berry phase.We theorize a unified description of the photonic SHE based on the two types of geometric phase gradient,and we experimentally measure the giant spin-dependent shift of the beam centroid produced by the metamaterial at a visible wavelength.Our results suggest that the structured metamaterial offers a potential method of manipulating spin-polarized photons and the orbital angular momentum of light and thus enables applications in spin-controlled nanophotonics.

Generation of arbitrary vector vortex beams on hybrid-order Poincaré sphere

We propose theoretically and verify experimentally a method of combining a q-plate and a spiral phase plate to generate arbitrary vector vortex beams on a hybrid-order Poincaré sphere. We demonstrate that a vector vortex beam can be decomposed into a vector beam and a vortex, whereby the generation can be realized by sequentially using a q-plate and a spiral phase plate. The generated vector beam, vortex, and vector vortex beam are verified and show good agreement with the prediction. Another advantage that should be pointed out is that the spiral phase plate and q-plate are both fabricated on silica substrates, suggesting the potential possibility to integrate the two structures on a single plate. Based on a compact method of transmissive-type transformation, our scheme may have potential applications in future integrated optical devices.

Polarization evolution of vector beams generated by q-plates

The polarization evolution of vector beams(VBs) generated by q-plates is investigated theoretically and experimentally.An analytical model is developed for the VB created by a general quarter-wave q-plate based on vector diffraction theory.It is found that the polarization distribution of VBs varies with position and the value q.In particular,for the incidence of circular polarization,the exit vector vortex beam has polarization states that cover the whole surface of the Poincarésphere,thereby constituting a full Poincarébeam.For the incidence of linear polarization,the VB is not cylindrical but specularly symmetric,and exhibits an azimuthal spin splitting.These results are in sharp contrast with those derived by the commonly used model,i.e.,regarding the incident light as a plane wave.By implementing q-plates with dielectric metasurfaces,further experiments validate the theoretical results.

All-angle reflectionless negative refraction with ideal photonic Weyl metamaterials

Negative refraction,an unnatural optical phenomenon in which the incident and the refracted waves reside on the same side of the surface normal,has been demonstrated with the invention of negative index media based on artificially engineered photonic structures called metamaterials.It has received wide attention due to its potential applications in imaging,nonlinear optics,and electromagnetic cloaking.However,it is highly challenging to realize negative refraction operating at all angles and with the perfect transmission.In this work,leveraging the recent development in topological photonics,we propose to realize reflection less negative refraction for all incident angles with a topological metamaterial.The proposed metamaterial possesses two Weyl points of opposite topological charges.By interfacing the metamaterial with a perfect electric conductor(PEC)or a perfect magnetic conductor(PMC),the Fermi arc connecting the two Weyl points can take the form of a half-circle possessing a positive or a negative refractive index.Importantly,due to the topological protection,there is no reflection at the interface between the PEC and PMC covered areas,leading to the observation of all-angle negative refraction without reflection at the boundary.Our work provides a new platform for manipulating the propagation of surface waves,which may find applications in the construction of integrated photonic devices.

Photonic Hall effect and helical Zitterbewegung in a synthetic Weyl system

Systems supporting Weyl points have gained increasing attention in condensed physics,photonics and acoustics due to their rich physics,such as Fermi arcs and chiral anomalies.Acting as sources or drains of Berry curvature,Weyl points exhibit a singularity of the Berry curvature at their core.It is,therefore,expected that the induced effect of the Berry curvature can be dramatically enhanced in systems supporting Weyl points.In this work,we construct synthetic Weyl points in a photonic crystal that consists of a honeycomb array of coupled rods with slowly varying radii along the direction of propagation.The system possesses photonic Weyl points in the synthetic space of two momenta plus an additional physical parameter with an enhanced Hall effect resulting from the large Berry curvature in the vicinity of the Weyl point.Interestingly,a helical Zitterbewegung(ZB)is observed when the wave packet traverses very close to a Weyl point,which is attributed to the contribution of the non-Abelian Berry connection arising from the near degenerate eigenstates.

CXorf67在PFA型室管膜瘤中作用及其机制的研究进展

CXorf67(chromosome X open reading frame 67)在绝大多数的细胞系以及成体组织和器官中均不表达,因而在很长时间内对这个蛋白质的研究和功能认识非常有限. 2018年,研究发现CXorf67特异性地在PFA(posterior fossa group A)亚型室管膜瘤中高表达,这开启了对CXorf67功能和机制的探索. PFA型室管膜瘤是9种室管膜瘤亚型中恶性程度和发病率最高的一种,这种亚型的肿瘤多发生于婴幼儿,由于缺少治疗药物以及缺乏有效的治疗策略,预后较差.目前的研究表明CXorf67可以通过抑制PRC2的活性和抑制DNA同源重组修复等不同机制在PFA型室管膜瘤中发挥功能,暗示其很可能是一个重要的用以发展靶向治疗的突破口.本文主要对目前发现的CXorf67功能及其机制进行了梳理和总结,并对潜在的PFA型室管膜瘤的治疗策略进行了探讨,为后续有待解决的科学问题进行了展望.