1,149 research outputs found
Topological Wannier cycles for the bulk and edges
Topological materials are often characterized by unique edge states which are
in turn used to detect different topological phases in experiments. Recently,
with the discovery of various higher-order topological insulators, such
spectral topological characteristics are extended from edge states to corner
states. However, the chiral symmetry protecting the corner states is often
broken in genuine materials, leading to vulnerable corner states even when the
higher-order topological numbers remain quantized and invariant. Here, we show
that a local artificial gauge flux can serve as a robust probe of the Wannier
type higher-order topological insulators which is effective even when the
chiral symmetry is broken. The resultant observable signature is the emergence
of the cyclic spectral flows traversing one or multiple band gaps. These
spectral flows are associated with the local modes bound to the artificial
gauge flux. This phenomenon is essentially due to the cyclic transformation of
the Wannier orbitals when the local gauge flux acts on them. We extend
topological Wannier cycles to systems with C2 and C3 symmetries and show that
they can probe both the bulk and the edge Wannier centers, yielding rich
topological phenomena
Oxidative stress promotes autophagic cell death in human neuroblastoma cells with ectopic transfer of mitochondrial PPP2R2B (Bβ2)
Bis[3-(pyrazin-2-yl)-5-(pyridin-2-yl-κN)-1,2,4-triazol-1-ido-κN 1]copper(II)
In the mononuclear title complex, [Cu(C11H7N6)2], the CuII atom lies on a crystallographic inversion centre and is coordinated by four N atoms from two bidentate chelate monoanionic 3-(pyrazin-2-yl)-5-(pyridin-2-yl-1,2,4-triazol-1-ido ligands, two from the triazolide rings [Cu—N = 1.969 (2) Å] and two from the pyridine rings [Cu—N = 2.027 (2) Å], giving a slightly distorted square-planar geometry
Observation of a phononic higher-order Weyl semimetal
Weyl semimetals are extraordinary systems where exotic phenomena such as
Fermi arcs, pseudo-gauge fields and quantum anomalies arise from topological
band degeneracy in crystalline solids for electrons and metamaterials for
photons and phonons. On the other hand, higher-order topological insulators
unveil intriguing multidimensional topological physics beyond the conventional
bulk-edge correspondences. However, it is unclear whether higher-order topology
can emerge in Weyl semimetals. Here, we report the experimental discovery of
higher-order Weyl semimetals in its phononic analog which exhibit
topologically-protected boundary states in multiple dimensions. We create the
physical realization of the higher-order Weyl semimetal in a chiral phononic
crystal with uniaxial screw symmetry. Using near-field spectroscopies, we
observe the chiral Fermi arcs on the surfaces and a new type of hinge arc
states on the hinge boundaries. These topological boundary arc states link the
projections of Weyl points in different dimensions and directions, and hence
demonstrate higher-order multidimensional topological physics in Weyl
semimetals. Our study establishes the fundamental connection between
higher-order topology and Weyl physics in crystalline materials and unveils a
new horizon of higher-order topological semimetals where unprecedented
materials such as higher-order topological nodal-lines may emerge
The Simulation and Experiment of a Non-Cross-Feeding Printed Log-Periodic Antenna
A non-cross-fed printed log-periodic antenna is simulated and studied experimentally. To avoid complex feeding with long coaxial line, the non-cross-feeding structure is applied in this antenna. The software CST Microwave Studio is employed to simulate the proposed antenna, and the optimized antenna model is obtained. According to the simulation results, the antenna prototype is produced and measured. Simulation and measured results show that the antenna is with S11<-10 dB in band of 4.2–9.2 GHz. And the radiation pattern and gain vary steadily in this band, which achieves requirements for wideband antenna. This antenna design can be extended to the design of the antenna integrated in communication circuit
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