13 research outputs found
Discovery of Higher-Order Nodal Surface Semimetals
The emergent higher-order topological insulators significantly deepen our
understanding of topological physics. Recently, the study has been extended to
topological semimetals featuring gapless bulk band nodes. To date, higherorder
nodal point and line semimetals have been successfully realized in different
physical platforms. However, the concept of higher-order nodal surface
semimetals, the final frontier in this field, has yet to be proposed, let alone
experimentally observed. Here, we report an ingenious design route for
constructing this unprecedented higher-order topological phase. The
threedimensional model, layer-stacked with two-dimensional anisotropic
SuSchrieffer-Heeger lattice, exhibits appealing hinge arcs connecting the
projected nodal surfaces. Experimentally, we realize this new topological phase
in an acoustic metamaterial, and present unambiguous evidence for both the bulk
nodal structure and hinge arc states, the two key manifestations of the
higher-order nodal surface semimetal. Our findings can be extended to other
classical systems such as photonic, elastic, and electric circuit systems, and
open new possibilities for controlling waves.Comment: 7 pages, 5 figure
Observation of Hybrid-Order Topological Pump in a Kekule-Textured Graphene Lattice
Thouless charge pumping protocol provides an effective route for realizing
topological particle transport. To date, the first-order and higher-order
topological pumps, exhibiting transitions of edge-bulk-edge and
corner-bulk-corner states, respectively, are observed in a variety of
experimental platforms. Here, we propose a concept of hybrid-order topological
pump, which involves a transition of bulk, edge, and corner states
simultaneously. More specifically, we consider a Kekul\'e-textured graphene
lattice that features a tunable phase parameter. The finite sample of zigzag
boundaries, where the corner configuration is abnormal and inaccessible by
repeating unit cells, hosts topological responses at both the edges and
corners. The former is protected by a nonzero winding number, while the latter
can be explained by a nontrivial vector Chern number. Using our skillful
acoustic experiments, we verify those nontrivial boundary landmarks and
visualize the consequent hybrid-order topological pump process directly. This
work deepens our understanding to higher-order topological phases and broadens
the scope of topological pumps.Comment: 5 figure
Acoustic Higher-Order Topological Insulators Protected by Multipole Chiral Numbers
Recently, the higher-order topological phases from the chiral AIII symmetry
classes are characterized by a Z topological invariant known as the multipole
chiral numbers, which indicate the number of degenerate zero-energy corner
states at each corner. Here, we report the first experimental realization of
higher-order topological insulators protected by multipole chiral numbers with
using acoustic crystals. Our acoustic measurements demonstrate unambiguously
the emergence of multiple corner states in the middle of the gap, as predicted
by the quantized multipole chiral numbers. Our study may provoke new
possibilities for controlling sound, such as acoustic sensing and energy
trapping
Geology and Petrogeochemistry of Lijiapuzi Nb-Ta Granitic Pegmatite Deposit: Implications for Ore Genesis and Prospecting
Most of the rare metal pegmatite deposits in China lie in West, Central and South China, and the Lijiapuzi Nb-Ta deposit is the only pegmatite-type Nb-Ta deposit in Northeast China, therefore a detailed study of the Lijiapuzi deposit is of great importance to the metallogeny and exploration of rare metal deposits in Northeast China. The Nb-Ta bearing pegmatites in Lijiapuzi district are composed of a microcline wall zone, a muscovite (lepidolite)-albite intermediate zone and a quartz core, and the rare metal mineralization mainly occurs in the intermediate zone and is intimately related to the albitization. The lithogeochemical features indicate that Lijiapuzi pegmatoids are rich in silicon and alkaline, poor in calcium, magnesium, titanium and phosphorus, and belong to peraluminous granitoid rocks. The enrichment of large ion lithophile elements (LILEs) and depletion of high field-strength elements (HFSEs), the distinct right-inclined REE pattern with obvious Eu negative anomaly, lower ratio of Nb/Ta and higher ratio of La/Nb and Rb/Sr indicate that the pegmatite was of a crustal origin and formed in relatively extensional tectonic setting of post-orogenesis. The pegmatites in Lijiapuzi area can be divided into two categories, i.e., the NW-trending pegmatites are shorter and thicker, with obvious zoning and localized in the upper part of the near-surface, while the NE-trending pegmatites are longer, thinner, devoid of zoning and localized in the lower part of the district. This probably means that excellent ore prospecting potential exists in the lower part of the Lijiapuzi district
BIF-hosted high-grade magnetite iron ore targeting by hyperspectral wavelength mapping of chlorite: case study of Qidashan Iron Mine, northeast China
There are two kinds of chlorites occurred in Anshan area, among which the hydrothermal Fe-chlorite with longer Fe-OH wavelength is spatially related to the high-grade magnetite ore, meaning that wavelength mapping of chlorites can be used to target the BIF-hosted high grade iron ore. In this article, quadratic polynomial, cubic spline, and quartic polynomial method were used to interpolate the absorption wavelength near 2250 nm of China ZY1-02D satellite hyperspectral image. The result of quadratic polynomial is continuous without data overlapping or intervals, thus most suitable for discrimination of the chlorites. The field truth shows that the spatial distribution of Fe-chlorite, validated by XRD analysis, is not only in accordance with that of high grade magnetite ore bodies, but also consistent with the recently discovered concealed iron bonanza. The study shows that hyperspectral remote sensing techniques can play significant role in the exploration of magnetite iron ore in east Liaoning Province
Effects of free-air CO2 enrichment (FACE) on N, P and K uptake of soybean in northern China
The objective of this study was to investigate the effect of elevated (550 ± 19 µmol mol−1) [CO2] on uptakeand utilization of nitrogen (N), phosphorus (P) and potassium (K) by soybean (Glycine max (L.) Merr) atthe free-air carbon dioxide enrichment (FACE) experimental facility in northern China. The above-ground biomass and root biomass were significantly increased under elevated [CO2]. Elevated [CO2] significantlydecreased the N concentration of the above-ground part at the beginning bloom (R1) stage, but had noeffect at the beginning pod (R3), beginning seed (R5) or harvest stage. The concentration of ureide inthe upper most fully-expanded leaf was not significantly affected by elevated [CO2] at any growth stage.Elevated [CO2] increased P concentration of the above-ground plant parts at the R1 and R5 stages, butdid not affect P concentration at the R3 stage or at harvest. However, K concentration of the above-ground plant parts and root was not affected by elevated [CO2] at any growth stage. At harvest, elevated [CO2] significantly increased N, P and K uptake in soybean seed. Results indicate that more N, P and Kfertilizers may be required to maintain the availability of these elements in the soil for soybean underfuture elevated [CO2] environments