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Superconductivity is caused by electron pairs that are canonically isotropic, whereas some exotic superconductors are known to exhibit non-trivial anisotropy stemming from unconventional pairings. However, superconductors with hexagonal symmetry, the highest rotational symmetry allowed in crystals, exceptionally have strong constraint that is called emergent rotational symmetry (ERS): anisotropic properties should be very weak especially near the critical temperature Tc even for unconventional pairings such as d-wave states. Here, we investigate superconducting anisotropy of the recently-found hexagonal Kagome superconductor CsV3Sb5, which is known to exhibit various intriguing phenomena originating from its undistorted Kagome lattice formed by vanadium atoms. Based on calorimetry performed under accurate two-axis field-direction control, we discover a combination of six- and two-fold anisotropies in the in-plane upper critical field. Both anisotropies, robust up to very close to Tc, are beyond predictions of standard theories. We infer that this clear ERS violation with nematicity is best explained by multi-component nematic superconducting order parameter in CsV3Sb5 intertwined with symmetry breakings caused by the underlying charge-density-wave order., 35 pages, 5 figures, 1 table, 7 extended figures

The transport and optical properties of the Nb-doped Cs(V$_{1-x}$Nb$_{x}$)$_{3}$Sb$_{5}$ with x = 0.03 and 0.07 have been investigated and compared with those of the undoped CsV$_{3}$Sb$_{5}$. Upon Nb doping, the charge-density wave (CDW) transition temperature $T_{\text{CDW}}$ is suppressed, and the superconducting temperature $T_{c}$ rises. The residual resistivity ratio decreases with Nb doping, suggesting an increase of disorder. For all compounds, the optical conductivity in the pristine phase reveals two Drude components (D1 and D2). The substitution of Nb causes an increase of D1 alongside a reduction of D2 in weight, which implies a change of the Fermi surface. The total Drude weight is reduced with increasing Nb content, signifying an enhancement of electronic correlations. Below $T_{\text{CDW}}$, while the optical conductivity clearly manifests the CDW gap in all materials, the gapped portion of the Fermi surface shrinks as the Nb content grows. A comprehensive analysis indicates that the change of the Fermi surface, the enhancement of electronic correlations, the shrinkage of the removed Fermi surface by the CDW gap, and the increase of disorder may all have a considerable impact on the interplay between the CDW and superconductivity in Cs(V$_{1-x}$Nb$_{x}$)$_{3}$Sb$_{5}$., 7 pages, 3 figures

Recently discovered kagome superconductors AV3Sb5 (A = K, Rb, Cs) exhibit exotic bulk and surface physical properties such as charge-density wave (CDW) and chirality, whereas their origins remain unresolved. By using micro-focused angle-resolved photoemission spectroscopy, we discovered that AV3Sb5 commonly exhibits two distinct polar surfaces depending on the termination; electron- and hole-doped ones for the A- and Sb-termination, respectively. We observed that the kagome-derived band shows a clear splitting in the A-terminated surface while it is absent in the Sb-terminated counterpart, indicative of the polarity-dependent CDW at the surface. Close comparison of the band-dependent splitting reveals that the three-dimensional CDW structure of the K-terminated surface is different from that of the Rb- or Cs-terminated surface, suggesting the diversity of the CDW ground state. These results provide important insight into the origin of CDW in kagome superconductors AV3Sb5., Comment: 10 pages, 8 figures

The Kagome material $A{\mathrm{V}}_3{\mathrm{Sb}}_5$ ($A$ = K, Rb, Cs) with geometry frustration hosts non-trivial topological electronic structures, electronic nematicity, charge density wave (CDW) and superconductivity, providing an ideal platform to study the interplay between these phases. Specifically, in pressurized- or substituted-${\mathrm{CsV}}_3{\mathrm{Sb}}_5$, the relationship between CDW and superconductivity is unusual and remains to be fully understood. Recently, coexisting and competing 2 $\times$ 2 $\times$ 4 and 2 $\times$ 2 $\times$ 2 CDW phases were discovered in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$. To investigate the evolution of the CDW phases with the substitution of V atoms, we performed x-ray diffraction (XRD) experiments on ${\mathrm{Cs(V}}_{1-x}{\mathrm{Ta}}_{x}{\mathrm{)}}_3{\mathrm{Sb}}_5$ and ${\mathrm{Cs(V}}_{1-x}{\mathrm{Nb}}_{x}{\mathrm{)}}_3{\mathrm{Sb}}_5$. Our results indicate that in all substituted samples, the discrete CDW reflection points in pristine ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ change to rod-like structures along the $c^\star$ direction. This suggests that the long-ranged three-dimensional CDW becomes quasi-two-dimensional by the substitution of V by Ta/Nb. Moreover, our temperature-dependent measurements show that there is no hysteresis behavior of CDW signals, indicating that the 2 $\times$ 2 $\times$ 4 CDW phase is easily suppressed by even a slight substitution of V with Nb/Ta. These findings uncover the CDW evolution upon substitution of V atoms in CsV$_3$Sb$_5$, providing insights into the microscopic mechanism of CDW and helping to understand the interplay between intertwined phases and superconductivity., Comment: 7 pages, 6 figures

Polar surface and interface play a pivotal role for realizing exotic properties of materials, and a search for such polar states is of crucial importance for expanding materials' functionality. Here we report micro-focused angle-resolved photoemission spectroscopy of CsV3Sb5, a member of recently discovered kagome superconductors AV3Sb5 (A = K, Rb, Cs), and show evidence for the polar nature of cleaved surface which is characterized by Cs- and Sb-terminated surfaces with markedly different fermiology. The Cs-terminated surface shows intriguing doubling of V-derived bands at low temperature associated with the band folding due to the three-dimensional charge-density wave (CDW), whereas the Sb-terminated one shows no band doubling or resultant CDW-gap opening indicative of the suppression of bulk-originated CDW due to polar charge. Such polar-surface-dependent band structure must be incorporated for understanding the origin of unconventional superconducting and charge order at the surface of AV3Sb5., 10 pages, 13 figures

カゴメ超伝導体CsV₃Sb₅は、TCDW = 94 K以下における2×2×2のCDW転移や、Tc = 2.5 Kでの超伝導転移に加えて、トポロジカルに非自明なバンド構造を有することが理論的に提案されるなど、カゴメ格子に由来する多彩な物性を示すことから、現在大きな注目を集めている。今回我々は、CsV₃Sb₅の物性発現機構の解明を目指して、KEK-PF BL-28AにおいてマイクロARPESを行い、3次元バンド構造を決定した。その結果、結合エネルギー0.5 eVに底を持つΓ点中心の電子的バンドや、K点において約0.3 eVに交点を持つディラックコーン型バンドなど複数の明瞭なバンド分散を観測した。, 第35回日本放射光学会年会・放射光科学合同シンポジウム

Kagome metals AV3Sb5 (A = K, Rb, and Cs) exhibit a unique superconducting ground state coexisting with charge-density wave (CDW), whereas how these characteristics are affected by carrier doping remains unexplored because of the lack of an efficient carrier-doping method. Here we report successful electron doping to CsV3Sb5 by Cs dosing, as visualized by angle-resolved photoemission spectroscopy. We found that the electron doping with Cs dosing proceeds in an orbital-selective way, as characterized by a marked increase in electron filling of the Sb 5pz and V 3dxz/yz bands as opposed to relatively insensitive nature of the V 3dxy/x2-y2 bands. By monitoring the temperature evolution of the CDW gap around the M point, we found that the CDW can be completely killed by Cs dosing while keeping the saddle point with the V 3dxy/x2-y2 character almost pinned at the Fermi level. The present result suggests a crucial role of multi-orbital effect to the occurrence of CDW, and provides an important step toward manipulating the CDW and superconductivity in AV3Sb5., Comment: 7 pages, 3 figures

The kagome metals $A$V$_{3}$Sb$_{5}$ ($A$ = K, Rb, Cs) have attracted enormous interest as they exhibit intertwined charge-density wave (CDW) and superconductivity. The alkali-metal dependence of these characteristics contains pivotal information about the CDW and its interplay with superconductivity. Here, we report optical studies of $A$V$_{3}$Sb$_{5}$ across the whole family. With increasing alkali-metal atom radius from K to Cs, the CDW gap increases monotonically, whereas $T_{\text{CDW}}$ first rises and then drops, at variance with conventional CDW. While the Fermi surface gapped by the CDW grows, $T_{c}$ is elevated in CsV$_{3}$Sb$_{5}$, indicating that the interplay between the CDW and superconductivity is not simply a competition for the density of states near \EF. More importantly, we observe an enhancement of electronic correlations in CsV$_{3}$Sb$_{5}$, which suppresses the CDW but enhances superconductivity, thus accounting for the above peculiar observations. Our results suggest electronic correlations as an important factor in manipulating the CDW and its entanglement with superconductivity in $A$V$_{3}$Sb$_{5}$., Comment: 6 pages, 4 figures. Comments are welcome and appreciated

The recently discovered coexistence of superconductivity and charge density wave order in the kagome systems AV3Sb5 (A = K, Rb, Cs) has stimulated enormous interest. According to theory, a vanadium-based kagome system may host a flat band, nontrivial linear dispersive Dirac surface states and electronic correlation. Despite intensive investigations, it remains controversial about the origin of the charge density wave (CDW) order, how does the superconductivity relate to the CDW, and whether the anomalous Hall effect (AHE) arises primarily from the kagome lattice or the CDW order. We report an extensive investigation on Cs(V1-xNbx)3Sb5 samples with systematic Nb doping. Our results show that the Nb doping induces apparent suppression of CDW order and promotes superconductivity; meanwhile, the AHE and magnetoresistance (MR) will be significantly weakened together with the CDW order. Combining with our density functional calculations, we interpret these effects by an antiphase shift of the Fermi energy with respect to the saddle points near M and the Fermi surface centered around {\Gamma}. It is found that the former depletes the filled states for the CDW instability and worsens the nesting condition for CDW order; while the latter lifts the Fermi level upward and enlarges the Fermi surface surrounding the {\Gamma} point, and thus promotes superconductivity. Our results uncover a delicate but unusual competition between the CDW order and superconductivity.

Kagome metals AV3Sb5 (A = K, Rb, and Cs) exhibit a characteristic superconducting ground state coexisting with charge-density wave (CDW), whereas the mechanisms of the superconductivity and CDW have yet to be clarified. Here we report a systematic ARPES study of Cs(V1-xNbx)3Sb5 as a function of Nb content x, where isovalent Nb substitution causes an enhancement of superconducting transition temperature (Tc) and the reduction of CDW temperature (TCDW). We found that the Nb substitution shifts the Sb-derived electron band at the Gamma point downward and simultaneously moves the V-derived band around the M point upward to lift up the saddle point (SP) away from the Fermi level, leading to the reduction of CDW-gap magnitude and TCDW. This indicates a primary role of the SP density of states to stabilize CDW. The present result also suggests that the enhancement of superconductivity by Nb substitution is caused by the cooperation between the expansion of the Sb-derived electron pocket and the recovery of the V-derived density of states at the Fermi level., Comment: 6 pages, 3 figures

Background. Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) has received increasing attention and application as an effective noninvasive mode of ventilation in the treatment of clinical anesthesia and critically ill patients. The conclusions reached in clinical studies of THRIVE and facemask oxygenation are still controversial, and the main objective of this systematic review is to determine the advantages of THRIVE over facemask oxygenation in intensive care units, respiratory medicine, and perioperative preoxygenation. Methods. PubMed, Embase, Web of Science, and Cochrane Library have search restrictions. The search library was full of English language articles from the first publication to 15 July 2021. Eligible randomized controlled study designs were included. 245 records were screened, and 5 studies met the inclusion criteria, enrolling a total of 235 patients. Results. Studying the THRIVE group compared to the facemask group, three studies analyzing intubation time showed that there is no difference in the effect of THRIVE and facemasks (MD -1.22, 95% CI -7.23 to 4.78, and P=0.69>0.05). Three studies analyzing apnea showed that there was no difference between the two groups (SMD 1, 95% CI -0.76 to 2.76, and P=0.27>0.05). Three studies analyzing PaO2 after preoxygenation showed that THRIVE is more effective than facemasks (MD 72.58, 95% CI 31.25 to 113.90, Z=3.44, and P0.05). Two studies analyzing PCO2 after complete paralysis or intubation preoxygenation showed that there was no difference between the two groups (MD 2.76, 95% CI -1.74 to 7.26, and P=0.23>0.05). Conclusions. THRIVE does not have a greater advantage over a facemask in improving apnea time, oxygenation time, PCO2, and SpO2, but it has an advantage in improving arterial partial pressure of oxygen (PaO2) after preoxygenation, which can improve PaO2 well. This trial is registered with the protocol registration number CRD42021268143.

In Kagome metal CsV$_3$Sb$_5$, multiple intertwined orders are accompanied by both electronic and structural instabilities. These exotic orders have attracted much recent attention, but their origins remain elusive. The newly discovered CsTi$_3$Bi$_5$ is a Ti-based Kagome metal to parallel CsV$_3$Sb$_5$. Here, we report angle-resolved photoemission experiments and first-principles calculations on pristine and Cs-doped CsTi$_3$Bi$_5$ samples. Our results reveal that the van Hove singularity (vHS) in CsTi$_3$Bi$_5$ can be tuned in a large energy range without structural instability, different from that in CsV$_3$Sb$_5$. As such, CsTi$_3$Bi$_5$ provides a complementary platform to disentangle and investigate the electronic instability with a tunable vHS in Kagome metals.

Linear nonsaturating magnetoresistance (LMR) represents a class of anomalous resistivity response to external magnetic field that has been observed in a variety of materials including but not limited to topological semi-metals, high-Tc superconductors and materials with charge/spin density wave (CDW/SDW) orders. Here we report the observation of LMR in layered kagome superconductor and CDW material CsV3Sb5 thin flakes, as well as the dimensional crossover and temperature (T) crossover of such LMR. Specifically, in ultrathin CsV3Sb5 crystals, the magnetoresistance (MR) exhibits a crossover from LMR at low T to quadratic B dependence above the CDW transition temperature; the MR also exhibits a crossover from LMR to sublinear MR for sample thickness at around ~20 nm at low T. We discuss several possible origins of the LMR and attribute the effect to two-dimensional (2D) CDW fluctuations. Our results may provide a new perspective for understanding the interactions between competing orders in kagome superconductors.

Room-temperature realization of macroscopic quantum phenomena is one of the major pursuits in fundamental physics. The quantum spin Hall state, a topological quantum phenomenon that features a two-dimensional insulating bulk and a helical edge state, has not yet been realized at room temperature. Here, we use scanning tunneling microscopy to visualize a quantum spin Hall edge state on the surface of the higher-order topological insulator Bi4Br4. We find that the atomically resolved lattice exhibits a large insulating gap of over 200meV, and an atomically sharp monolayer step edge hosts a striking in-gap gapless state, suggesting the topological bulk-boundary correspondence. An external magnetic field can gap the edge state, consistent with the time-reversal symmetry protection inherent to the underlying topology. We further identify the geometrical hybridization of such edge states, which not only attests to the Z2 topology of the quantum spin Hall state but also visualizes the building blocks of the higher-order topological insulator phase. Remarkably, both the insulating gap and topological edge state are observed to persist up to 300K. Our results point to the realization of the room-temperature quantum spin Hall edge state in a higher-order topological insulator.

最近発見されたカゴメ超伝導体CsV3Sb5は、TCDW = 94 K以下における2×2×2のCDW転移や、Tc = 2.5 Kでの超伝導転移に加えて、トポロジカルに非自明なバンド構造を有することが理論的に提案されるなど、カゴメ格子に由来する多彩な物性を示すことから、現在大きな注目を集めている。今回我々は、CsV3Sb5の物性発現機構の解明を目指して、KEK-PF BL-28AにおいてマイクロARPESを行い、3次元バンド構造を決定した。その結果、結合エネルギー0.5 eVに底を持つΓ点中心の電子的バンドや、K点において約0.3 eVに交点を持つディラックコーン型バンドなど複数の明瞭なバンド分散を観測した。, 日本物理学会 2021年秋季大会

The combination of topology and magnetism is attractive to produce exotic quantum matters, such as the quantum anomalous Hall state, axion insulators and the magnetic Weyl semimetals. MnBi2Te4, as an intrinsic magnetic topological insulator, provides a platform for the realization of various topological phases. Here we report the intermediate Hall steps in the magnetic hysteresis of MnBi2Te4, where four distinguishable magnetic memory states at zero magnetic field are revealed. The gate and temperature dependence of the magnetic intermediate states indicates the noncollinear spin structure in MnBi2Te4, which can be attributed to the Dzyaloshinskii-Moriya interaction as the coexistence of strong spin-orbit coupling and local inversion symmetry breaking on the surface. Moreover, these multiple magnetic memory states can be programmatically switched among each other through applying designed pulses of magnetic field. Our results provide new insights of the influence of bulk topology on the magnetic states, and the multiple memory states should be promising for spintronic devices.

Water flooding type-curves, recently receiving increasing attentions, play an essential role in evaluation of OOIP and prediction of future production. The study proposed a method modified form Weibull model and water flooding type-curves to analyze the reservoir production performance, including predication of oil production and water injection rates. The results indicate that the method can estimate and provide solutions for oil production, water injection rate and injection-production ratio with a well accuracy. A case study is conducted to demonstrate the applicability and accuracy of model by field data. The matching results illustrate a good accordance between calculated values and field data. Keywords: Weibull model, Water flooding type-curves, Oil production, Water injection rate, Injection-production ratio

In this work, a new crystal growth technique called the liquid transport method was introduced to synthesize single crystals of a topological superconductor candidate, InxSn1−xTe (IST). Crystals with the size of several millimeters were successfully synthesized, and were characterized by X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy as well as electronic transport measurements. Lattice parameters decreased monotonously with the increase of indium content while hole density varied in reverse. Superconductivity with the critical temperature (Tc) around 1.6 K were observed, and the hole densities were estimated to be in the order of 1020 cm−3. The upper critical fields (Bc2) were estimated to be 0.68 T and 0.71 T for In0.04Sn0.96Te and In0.06Sn0.94Te, respectively. The results indicated that the quality of our crystals is comparable to that grown by the chemical vapor transport method, but with a relatively larger size. Our work provides a new method to grow large single crystals of IST and could help to solve the remaining open questions in a system that needs large crystals, such as a superconducting pairing mechanism, unconventional superconductivity, and so on.

We report on a detailed study of the optical properties of CsV$_{3}$Sb$_{5}$ at a large number of temperatures above and below the charge-density-wave (CDW) transition. Above the CDW transition, the low-frequency optical conductivity reveals two Drude components with distinct widths. An examination of the band structure allows us to ascribe the narrow Drude to multiple light and Dirac bands, and the broad Drude to the heavy bands near the $M$ points which form saddle points near the Fermi level. Upon entering the CDW state, the opening of the CDW gap is clearly observed. A large portion of the broad Drude is removed by the gap, whereas the narrow Drude is not affected. Meanwhile, an absorption peak associated with interband transitions near the saddle points shifts to higher energy and grows in weight. These observations are consistent with the scenario that the CDW in CsV$_{3}$Sb$_{5}$ is driven by nesting of Fermi surfaces near the saddle points at $M$., 6 pages, 2 figures. Comments are welcome and appreciated

Kagome superconductors with TC up to 7 K have been discovered for over 40 y. Recently, unconventional chiral charge order has been reported in kagome superconductor KV3Sb5, with an ordering temperature of one order of magnitude higher than the TC. However, the chirality of the charge order has not been reported in the cousin kagome superconductor CsV3Sb5, and the electronic nature of the chirality remains elusive. In this paper, we report the observation of electronic chiral charge order in CsV3Sb5 via scanning tunneling microscopy (STM). We observe a 2 × 2 charge modulation and a 1 × 4 superlattice in both topographic data and tunneling spectroscopy. 2 × 2 charge modulation is highly anticipated as a charge order by fundamental kagome lattice models at van Hove filling, and is shown to exhibit intrinsic chirality. We find that the 1 × 4 superlattices form various small domain walls, and can be a surface effect as supported by our first-principles calculations. Cru- cially, we find that the amplitude of the energy gap opened by the charge order exhibits real-space modulations, and features 2 × 2 wave vectors with chirality, highlighting the electronic nature of the chiral charge order. STM study at 0.4 K reveals a superconducting energy gap with a gap size 2􏰀 = 0.85 meV , which estimates a moderate superconductivity coupling strength with 2􏰀/kBTC = 3.9. When further applying a c-axis magnetic field, vortex core bound states are observed within this gap, indicative of clean-limit superconductivity. Nanyang Technological University National Research Foundation (NRF) Accepted version The work at Beijing Institute of Technology was sup- ported by the National Key R&D Program of China (Grant No. 2020YFA0308800), the Natural Science Foun- dation of China (Grants No. 92065109, No. 11734003, and No. 12061131002), the Beijing Natural Science Foundation (Grant No. Z190006), and the Beijing Institute of Technology (BIT) Research Fund Program for Young Scholars (Grant No. 3180012222011). Z.W. thanks the Analysis & Testing Center at BIT for assistance in facility support. Experimental and theoretical work at Princeton University was supported by the Gordon and Betty Moore Foundation [Grants No. GBMF4547 and No. GBMF9461 (M.Z.H.)]. Y.S. was supported by the National Natural Science Foundation of China (Grant No. U2032204), and the K. C. Wong Education Foundation (Grant No. GJTD-2018-01). G.C. would like to acknowledge the support of the National Research Foundation, Singapore under its NRF Fellowship Award No. NRF-NRFF13-2021- 0010 and the Nanyang Assistant Professorship grant from Nanyang Technological University. P.D. is supported the U.S. Department of Energy (DOE), Basic Energy Sciences (BES), under Contract No. DE-SC0012311. S.S. and Y.W. were supported by the National Natural Science Foundation of China under Grants No. 11822404 and No. 11774127.

Compounds with kagome lattice usually host many exotic quantum states, including the quantum spin liquid, non-trivial topological Dirac bands and a strongly renormalized flat band, etc. Recently an interesting vanadium based kagome family $A$V$_{3}$Sb$_{5}$ ($A$ = K, Rb, or Cs) was discovered, and these materials exhibit multiple interesting properties, including unconventional saddle-point driving charge density wave (CDW) state, superconductivity, etc. Furthermore, some experiments show anomalous Hall effect which inspires that there might be some chiral flux current states. Here we report scanning tunneling measurements by using spin-polarized tips. Although we have observed clearly the $2a_0\times2a_0$ CDW and $4a_0$ stripe orders, the well-designed experiments with refined spin-polarized tips do not reveal any trace of the chiral flux current phase in CsV$_3$Sb$_5$ within the limits of experimental accuracy. No observation of the local magnetic moment in our experiments may put an upper bound constraint on the magnitude of magnetic moments induced by the possible chiral loop current which has a time-reversal symmetry breaking along $c$-axis in CsV$_{3}$Sb$_{5}$., Comment: 10 pages, 4 figures

Kagome superconductors with Tc up to 7K have been discovered over 40 years. Recently, unconventional chiral charge order has been reported in kagome superconductor KV3Sb5, with an ordering temperature of one order of magnitude higher than the TC. However, the chirality of the charge order has not been reported in the cousin kagome superconductor CsV3Sb5, and the electronic nature of the chirality remains elusive. In this letter, we report the observation of electronic chiral charge order in CsV3Sb5 via scanning tunneling microscopy (STM). We observe a 2x2 charge modulation and a 1x4 superlattice in both topographic data and tunneling spectroscopy. 2x2 charge modulation is highly anticipated as a charge order by fundamental kagome lattice models at van Hove filling, and is shown to exhibit intrinsic chirality. We find that the 1x4 superlattices forms various small domain walls, and can be a surface effect as supported by our first-principles calculations. Crucially, we find that the amplitude of the energy gap opened by the charge order exhibits real space modulations, and features 2x2 wave vectors with chirality, highlighting the electronic nature of the chiral charge order. STM study at 0.4K reveals a superconducting energy gap with a gap size 2{\Delta}=0.85meV, which estimates a moderate superconductivity coupling strength with 2{\Delta}/kBTc=3.9. When further applying a c-axis magnetic field, vortex core bound states are observed within this gap, indicative of clean-limit superconductivity.

Kagome metals AV3Sb5 (A = K, Rb, and Cs) exhibit superconductivity at 0.9-2.5 K and charge-density wave (CDW) at 78-103 K. Key electronic states associated with the CDW and superconductivity remain elusive. Here, we investigate low-energy excitations of CsV3Sb5 by angle-resolved photoemission spectroscopy. We found an energy gap of 70-100 meV at the Dirac-crossing points of linearly dispersive bands, pointing to an importance of spin-orbit coupling. We also found a signature of strongly Fermi-surface and momentum-dependent CDW gap characterized by the larger energy gap of maximally 70 meV for a band forming a saddle point around the M point, the smaller (0-18 meV) gap for a band forming massive Dirac cones, and a zero gap at the Gamma-centered electron pocket. The observed highly anisotropic CDW gap which is enhanced around the M point signifies an importance of scattering channel connecting the saddle points, laying foundation for understanding the nature of CDW and superconductivity in AV3Sb5., Comment: 10 pages, 9 figures

Two-dimensional topological insulator features time-reversal-invariant spin-momentum-locked one-dimensional (1D) edge states with a linear energy dispersion. However, experimental access to 1D edge states is still of great challenge and only limited to few techniques to date. Here, by using infrared absorption spectroscopy, we observed robust topologically originated edge states in a-Bi4Br4 belts with definitive signature of strong infrared absorption at belt sides and distinct anisotropy with respect to light polarizations, which is further supported by first-principles calculations. Our work demonstrates for the first time that the infrared spectroscopy can offer a power-efficient approach in experimentally probing 1D edge states of topological materials., Comment: 15 pages, 5 figures, 29 references

Sometimes, the high-resolution A/D or D/A converter all need a high precision reference, the voltage of reference will determine the precision of the conversion result. In whole system, it always requires that the conversion result should be in a specified range in a wide temperature range. In order to release the variation range of conversion result, it requires that the temperature coefficient of reference should be very small. In this paper, it introduces one higher order compensated band-gap reference, it uses the current $\mathrm{I}_{\mathrm{b}}$ from the existing structure to compensate the higher-order voltage of $\mathbf{V}_{\mathrm{BE}}$ . In this way, the temperature coefficient of this Band-Gap Reference will be less than 1ppm/°C in theory.

Sometimes, the input-port of A/D converter always needs a S/H switch. In Sample state, the S/H switch should always be opening, now voltages between input-port and output-port in S/H switch are always the same. In Hold state, the S/H switch should always be closing, now the voltage of output-port in S/H switch will keep a fixed value, and it will not be changed with the voltage of input-port in S/H switch. For A/D converter, the conversion linearity is the most important parameter. For getting the best performance of conversion linearity, it is very important to design a high linear S/H switch. In sample stage, the voltage of output-port in S/H switch should be always changed with the voltage of input-port at any time. It is very easy to S/H switch design under the normal condition. Next for getting the higher linear performance in A/D converter, the fixed value in Hold state should be keeping linear performance of input voltage at the most, it is very hard in high resolution A/D converter. Through this paper's design, it makes the distortion leading by Sample switch become linear distortion. So it can get a high performance S/H bootstrapped switch, which can apply to 16-bit or much higher resolution ADC.

The rapid development of location-based service (LBS) drives one special kind of LBS, in which the service provider verifies user location before providing services. In distributed location proof generating schemes, preventing users from colluding with each other to create fake location proofs and protecting user's location privacy at the same time, are the main technical challenges to bring this kind of LBS into practical. Existing solutions tackle these challenges with low collusion-detecting efficiency and defected collusion-detecting method. We proposed two novel location proof generating schemes, which inversely utilized a secure secret-sharing scheme and a pseudonym scheme to settle these shortcomings. Our proposed solution resists and detects user collusion attacks in a more efficient and correct way. Meanwhile, we achieve a higher level of location privacy than that of previous work. The correctness and efficiency of our proposed solution is testified by intensive security analysis, performance analysis, as well as experiments and simulation results.

In SAR ADC, the capacitance array is a very important unit, it will determine the conversion performance in whole ADC. In L-bit SAR ADC, the resolution of the capacitance array must should be larger than L-bit. For getting a smaller layout area, the main body frame of capacitance array uses the M+N bit sectional type, but in traditional design schematic, the least N bit sectional capacitance array’ parasitic capacitance will directly reduce the conversion precision. At the same time, the bridging capacitor will be not equal to the unit capacitor. In this improved design, for solving those problems, this paper improves the least N bit sectional capacitor array, letting the bridging capacitor also constituted by unit capacitors, and this capacitance array also can ignore the parasitic capacitors at anywhere. So in this paper, the whole capacitor array all uses the unit capacitors to get the high matching precision performance, at the same time, in this improved design, the parasitic capacitors at the anywhere all could not reduce the conversion resolution of the capacitance array.

In SAR ADC, the capacitance array is a very important unit, it will determine the conversion performance in whole ADC. In 12-bit SAR ADC, the matching precision of the capacitor array must should be larger than 12-bit. But in normal semiconductor foundry, the high matching precision capacitor array almost should be constituted by unit capacitors. This paper introduces a new design, for getting a smaller layout area, the main body frame of capacitor array uses the M+N bit sectional type, but in traditional design schematic, the bridging capacitor will be not equal to the unit capacitor. In this improved design, for solving this problem, this paper improves the least N bit sectional capacitor array, letting the bridging capacitor also constituted by unit capacitors. So in this paper, the whole capacitor array all uses the unit capacitors to get the high matching precision performance.

This paper presents a new method of injection-production allocation estimation for water-flooding mature oilfields. The suggested approach is based on logistic growth rate functions and several type-curve matching methods. Using the relationship between these equations, oil production and water injection rate as well as injection-production ratio can be easily forecasted. The calculation procedure developed and outlined in this paper requires very few production data and is easily implemented. Furthermore, an oilfield case has been analyzed. The synthetic and field cases validate the calculation procedure, so it can be accurately used in forecasting production data, and it is important to optimize the whole injection-production system.

This paper designs a kind of numerical control machine for polishing the glasses frame. This CNC machine adopts the structure of the five-axis gantry machining center, mainly including X/Y/Z three-axis gantry movement platform and R/S two-axis rotary motion system. This paper uses 3D software to create the three-dimensional model of the machine, and then uses the finite element analysis software ANSYS to make modal analysis of the whole machine tool structure and get the inherent frequency and vibration mode to analyze the corresponding dynamic performance. Based on the modal analysis, this paper evaluates the mechanical properties of machine tool and provides the theoretical basis for design and improvement of the machine

In SAR ADC, the capacitance array is a very important unit, it will determine the conversion performance of the whole ADC. In normal semiconductor foundry, the matching precision of the linear capacitor is always about 10 bit, so it is not impossible to realize the 16-bit conversion precision in normal COMS foundry. This paper introduces a new design, for getting a smaller layout area, the main body frame of capacitor array uses the M+N+L bit sectional type; For getting the high matching precision performance, the lower bridging capacitor will be the normalized capacitor; For getting the high conversion precision, all the Upper-Bit in capacitance array will add a sub-calibrated capacitor array. So in this paper, it uses the circuit structure to realize the high precision capacitor array in 16-bit SAR ADC.

The rapid development of mobile technology has improved users’ quality of treatment, and tremendous amounts of medical information are readily available and widely used in data analysis and application, which bring on serious threats to users’ privacy. Classical methods based on cryptography and anonymous-series models fail due to their high complexity, poor controllability, and dependence on the background knowledge of adversaries when it comes to current mobile healthcare applications. Differential privacy is a relatively new notion of privacy and has become the de facto standard for a security-controlled privacy guarantee. In this paper, the key aspects of basic concepts and implementation mechanisms related to differential privacy are explained, and the existing research results are concluded. The research results presented include methods based on histograms, tree structures, time series, graphs, and frequent pattern mining data release methods. Finally, shortcomings of existing methods and suggested directions for future research are presented.