Synthetic gauge fields enable high-order topology on Brillouin real projective plane

The topology of the Brillouin zone, foundational in topological physics, is always assumed to be a torus. We theoretically report the construction of Brillouin real projective plane ($\mathrm{RP}^2$) and the appearance of quadrupole insulating phase, which are enabled by momentum-space nonsymmorphic symmetries stemming from $\mathbb{Z}_2$ synthetic gauge fields. We show that the momentum-space nonsymmorphic symmetries quantize bulk polarization and Wannier-sector polarization nonlocally across different momenta, resulting in quantized corner charges and an isotropic binary bulk quadrupole phase diagram, where the phase transition is triggered by a bulk energy gap closing. Under open boundary conditions, the nontrivial bulk quadrupole phase manifests either trivial or nontrivial edge polarization, resulting from the violation of momentum-space nonsymmorphic symmetries under lattice termination. We present a concrete design for the $\mathrm{RP}^2$ quadrupole insulator based on acoustic resonator arrays and discuss its feasibility in optics, mechanics, and electrical circuits. Our results show that deforming the Brillouin manifold creates opportunities for realizing high-order band topology.Comment: 5 pages,5 figure

Tris(2-formylphenolato-κ2O,O′)(1,10-phenanthroline-κ2N,N′)samarium(III)

In the title compound, [Sm(C7H5O2)3(C12H8N2)], the SmIII cation is coordinated by six O atoms from three bidentate 2-formylphenolate ligands and by two N atoms from 1,10-phenanthroline ligand. The resulting SmN2O6 coordination polyhedron is a distorted square antiprism. In the crystal, C—H...O interactions connect molecules into chains along the b-axis direction. In addition, π–π stacking interactions are observed with centroid–centroid distances in the range 3.6422 (13)–3.7329 (13) Å

A case of repeated intracerebral hemorrhages secondary to ventriculoperitoneal shunt

Ventriculoperitoneal shunt is a routinely performed treatment in neurosurgical department. Intracerebral hemorrhage, as a complication after shunt catheterization, is really rare but with high mortality. In this study, we reported a case of a 74-year-old man who suffered from repeated intracerebral hemorrhage after ventriculoperitoneal shunt. The first hemorrhage happened 63 h after the 1st surgery, and most hematomas were located in the ipsilateral occipital lobe and intraventricles, along the ventricular catheter. Fresh blood clot casts blocked the external ventricular draining catheter, which was inserted into the right front horn during the 3rd surgery, indicating new intraventricular bleeding happened. A large hematoma in ipsilateral frontal lobe was detected on the 3rd day after the removal of external ventricular draining catheter. Different hemorrhagic locations and time points were encountered on the same case. We discussed the possible causes of repeated hemorrhage for this case, and the pre-operative preparation including risk evaluation in future clinical work

Generation and regularization of zigzag focal conic domains guided by thermodynamic-driven topological defect evolution

Liquid crystals, as typical anisotropic building blocks, tend to self-assemble into various ordered architectures during distinct thermodynamic processes. Research on the underlying mechanisms and rules may drastically promote our understanding of complicated structures. Here, zigzag focal conic domains (ZFCDs) are generated in rapid cooling process under an antagonistic boundary condition. After several thermal cycles beneath the nematic-smectic (N-S) phase transition point, the ZFCDs are well regularized. We found that the dislocations associated with the rapid cooling play vital roles in the formation of ZFCDs. A strong interphase correlation between the zigzag ± 1/2 disclination pairs and ZFCDs is observed above the N-S phase transition point. The orientational order inheritance and topological invariance across the phase transition indicate that similar disclination pairs exist in ZFCDs. These disclination pairs facilitate the opposite tilt direction and a half-pitch lateral shift between neighboring focal conic domains (FCDs), thus forming ZFCDs. During thermal cycles, the thermal motion of molecules induces the regularization and elimination of defect cores, further resulting in the ordered ZFCDs. Via properly controlling the cooling rate, large-area ordered ZFCDs are achieved in a wide film thickness range after thermal cycles. This study enriches the knowledge on the topological defect guided architecture of liquid crystals and may pave the way for the generation and regularization of ordered self-assembled systems

Generation and high-resolution imaging of higher-order polarization via metasurface

The generation and focusing properties of higher-order polarized beams have attracted lots of interests due to its significant applications. In this paper,we derived the formula of transforming linear polarization into higher-order polarization, which is applicable to generating arbitrary order polarization. Based on the derived formula, the focusing properties of higher-order polarization by dielectric metasurface lens are studied , which exhibit an Abbe-limit-breaking feature for small numerical aperture, i.e., NA<0.6. When a binary phase (0 & {\pi}) is further imposed on the aperture of metasurface lens, the focusing spot of fourth-order polarization breaks Abbe limit even by 14.3% at NA= 0.6. In addition, the effect of fabrication tolerance, say, substrate thickness and central deviation, on the focusing feature of higher-order polarization is also investigated. Our study may find significant applications in achieving higher-resolution lithography and imaging, say, by just replacing conventional linear or circular polarization with higher-order polarization