Search

Your search keyword '"Weng, Y. X."' showing total 14 results
Start Over Author "Weng, Y. X."
14 results on '"Weng, Y. X."'

1. Superconductivity in HfTe5 Induced via Pressures

Author

Liu, Y., Long, Y. J., Zhao, L. X., Nie, S. M., Zhang, S. J., Weng, Y. X., Jin, M. L., Li, W. M., Liu, Q. Q., Long, Y. W., Yu, R. C., Fen, X. L., Li, Q., Weng, H. M., Dai, X., Fang, Z., Chen, G. F., and Jin, C. Q.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons
Abstract

Recently, ZrTe5 and HfTe5 are theoretically studied to be the most promising layered topological insulators since they are both interlayer weakly bonded materials and also with a large bulk gap in the single layer. It paves a new way for the study of novel topological quantum phenomenon tuned via external parameters. Here, we report the discovery of superconductivity and properties evolution in HfTe5 single crystal induced via pressures. Our experiments indicated that anomaly resistance peak moves to low temperature first before reverses to high temperature followed by disappearance which is opposite to the low pressure effect on ZrTe5. HfTe5 became superconductive above ~5.5 GPa up to at least 35 GPa in the measured range. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. High pressure Raman revealed that new modes appeared around pressure where superconductivity occurs. Crystal structure studies shown that the superconductivity is related to the phase transition from Cmcm structure to monoclinic C2/m structure. The second phase transition from C2/m to P-1 structure occurs at 12 GPa. The combination of transport, structure measurement and theoretical calculations enable a completely phase diagram of HfTe5 at high pressures., Comment: 19 pages+8 Figures with supplementary materials

Published
2016

2. Superconductivity in HfTe5 across weak to strong topological insulator transition induced via pressures

Author

Liu, Y., primary, Long, Y. J., additional, Zhao, L. X., additional, Nie, S. M., additional, Zhang, S. J., additional, Weng, Y. X., additional, Jin, M. L., additional, Li, W. M., additional, Liu, Q. Q., additional, Long, Y. W., additional, Yu, R. C., additional, Gu, C. Z., additional, Sun, F., additional, Yang, W. G., additional, Mao, H. K., additional, Feng, X. L., additional, Li, Q., additional, Zheng, W. T., additional, Weng, H. M., additional, Dai, X., additional, Fang, Z., additional, Chen, G. F., additional, and Jin, C. Q., additional

Published
2017
Full Text
View/download PDF

5. Direct Observation of Mass Transfer at Solid−Liquid Interface by Laser Flash Photolysis of the Interface Probe Molecules

Author

Weng, Y.-X., Xiao, H., Chan, K.-C., and Che, C.-M.

Abstract

Transient absorption signal delayed by a magnitude of 100 μs with respect to the exciting laser shot is observed after UV laser flash photolysis of degassed benzene, acetone, and acetonitrile solutions of an interface probe complex, i.e., gold(I) complex [{Au[P(C6H4OMe-p)3]}2-(μ-C≡C)] ([μ-ethynylene-bis{tris(4-methoxyphenyl)phosphine}gold]). Chemical reactions leading to the transient absorbance change are confirmed to be occurring at the solid−liquid interface, and the delay time is believed to arise from the photogenerated intermediate species in the bulk solution crossing the diffusion layer, which ultimately undergo interfacial reactions resulting in the observed transient absorbance change. The delay time is suggested as a direct measure for the thickness of the diffusion layer. The thickness of the diffusion layer around 0.2 μm, estimated by this method, is comparable to that from the sonovoltammetric study. Oscillations in transient absorbance kinetics are also observed, which can be attributed to the coupling between the interfacial chemical reactions and a photoacoustic effect; oscillation due to a single physical process arising from the schlieren effect under certain condition is also discussed. Similar transient phenomena are observed in another luminescent complex, i.e., a hexanuclear Cu(I) cluster Cu6(t-NS)6 (t-NS = 4-tert-butylpyridine-2-thiolate). The characterization of the photochemical reaction processes of the Cu(I) complex by means of transient absorbance difference spectra reveals that a consecutive biphotonic ionization process occurs after the laser flash. The intermediate species with a lifetime of 65 μs responsible for the interfacial reaction is tentatively assigned as a charge separation pair. A reaction scheme involving surface-assisted ionization of the charge separation pair is proposed to account for the coupling between the interfacial chemical reaction and the photoacoustic effect.

Published
2000

6. Back Electron Transfer from TiO<INF>2</INF> Nanoparticles to Fe<SUP>III</SUP>(CN)<INF>6</INF><SUP>3-</SUP>:  Origin of Non-Single-Exponential and Particle Size Independent Dynamics

Author

Weng, Y.-X., Wang, Y.-Q., Asbury, J. B., Ghosh, H. N., and Lian, T.

Abstract

Back-electron-transfer (ET) dynamics in FeII(CN)64--sensitized colloidal TiO2 nanoparticles are studied using ultrafast pump probe spectroscopy. Excitation of the adsorbate-to-nanoparticle charge-transfer band at 400 nm leads to direct injection of electrons from FeII(CN)64- to TiO2. The kinetics of back electron transfer from TiO2 to the FeIII(CN)63- are measured by monitoring the bleach recovery of the charge-transfer band in the 430−600 nm region. The measured back-ET kinetics are non-single-exponential, and a multiexponential fit requires at least four components on the &lt;1 ns time scale. The kinetics are independent of pump power, indicating a geminate recombination process. Recombination kinetics are very similar in two samples of 5 and 11 nm (A-type) particles prepared from dried nanoparticle powder, but they are noticeably different from those in samples of 3 and 9 nm (B-type) nanoparticles prepared directly from colloids without drying. This result indicates that the back-ET kinetics in this system are more influenced by the surface properties of the nanoparticles than their sizes. Two models with different distributions of trapped electrons are used to describe the back-ET kinetics. Model I assumes a homogeneous distribution of electrons on the surface of the entire particle. This model predicts a large particle size dependence and cannot fit the observed kinetics. Model II assumes a more localized distribution of injected electrons and takes account of relaxation from shallow to deep trap states during the recombination process. This model can fit the back-ET kinetics with three fitting parameters. According to this model, the injected electrons are trapped near the adsorbate, which accounts for the size independent back-ET kinetics. This model also predicts that trapped electrons at longer distance and/or larger trap energy recombine slower. A distribution of distance and trap energy as well as relaxation between trap states give rise to multiexponential back-ET kinetics.

Published
2000

7. Interfacial potential and photoelectronic properties of manganite heterojunction La0.7Ce0.3MnO3/SrTiO3:Nb.

Author

Sun, J. R., Shen, B. G., Tian, H. F., Li, J. Q., and Weng, Y. X.

Subjects
HETEROJUNCTIONS, HETEROSTRUCTURES, SEMICONDUCTOR junctions, TRANSMISSION electron microscopes, MANGANITE, ELECTRON microscopes, SEMICONDUCTORS
Abstract

The interfacial potential and photoelectronic properties of a heterojunction composed of La0.7Ce0.3MnO3 and SrTiO3:Nb have been experimentally studied. A two-dimensional spatial distribution of the electrostatic potential across the La0.7Ce0.3MnO3/SrTiO3:Nb interface is obtained by the holography technique of the transmission electron microscope, which reveals the presence of a depletion layer of 8 nm in thickness at 120 K and 3 nm at 296 K and a built-in electric field within this layer. Consequently, a complex yet significant photovoltaic effect is observed. It is found that the transient photocurrent is composed of two distinctive processes with the charging-like behavior, and the time constants are surprisingly larger than that expected for a photoelectronic process, ∼30 and ∼260 μs, respectively. It seems to be an intrinsic property of the manganite junction, and has nothing to do with external circuit and thermolelectric effect arising from light illumination. [ABSTRACT FROM AUTHOR]

Published
2005
Full Text
View/download PDF

11. Superconductivity in HfTe5 across weak to strong topological insulator transition induced via pressures.

Author

Liu, Y., Long, Y. J., Zhao, L. X., Nie, S. M., Zhang, S. J., Weng, Y. X., Jin, M. L., Li, W. M., Liu, Q. Q., Long, Y. W., Yu, R. C., Gu, C. Z., Sun, F., Yang, W. G., Mao, H. K., Feng, X. L., Li, Q., Zheng, W. T., Weng, H. M., and Dai, X.

Abstract

Recently, theoretical studies show that layered HfTe5 is at the boundary of weak &strong topological insulator (TI) and might crossover to a Dirac semimetal state by changing lattice parameters. The topological properties of 3D stacked HfTe5 are expected hence to be sensitive to pressures tuning. Here, we report pressure induced phase evolution in both electronic &crystal structures for HfTe5 with a culmination of pressure induced superconductivity. Our experiments indicated that the temperature for anomaly resistance peak (Tp) due to Lifshitz transition decreases first before climbs up to a maximum with pressure while the Tp minimum corresponds to the transition from a weak TI to strong TI. The HfTe5 crystal becomes superconductive above ~5.5 GPa where the Tp reaches maximum. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. Crystal structure studies indicate that HfTe5 transforms from a Cmcm phase across a monoclinic C2/m phase then to a P-1 phase with increasing pressure. Based on transport, structure studies a comprehensive phase diagram of HfTe5 is constructed as function of pressure. The work provides valuable experimental insights into the evolution on how to proceed from a weak TI precursor across a strong TI to superconductors. [ABSTRACT FROM AUTHOR]

Published
2017
Full Text
View/download PDF

12. [Clinical characteristics and prognostic risk factors analysis of carbapenem-resistant organism in the department of hematology].

Author

Chen SZ, Xu JJ, Xiao TT, Weng YX, Chen DB, Zhang Y, Ren JH, Luo XF, Zheng ZH, Zheng XY, Chen ZZ, Hu JD, and Yang T

Subjects
Anti-Bacterial Agents pharmacology, Anti-Bacterial Agents therapeutic use, Humans, Microbial Sensitivity Tests, Prognosis, Retrospective Studies, Risk Factors, Carbapenems pharmacology, Hematology
Abstract

Objective: To study the distribution and drug resistance of Carbapenem-Resistant Organism (CRO) and to analysis the risk factors of CRO 30-day mortality. Methods: A total of 181 patients with CRO infection diagnosed in Department of Hematology, Fujian Medical University Union Hospital from January 2018 to June 2020 were retrospectively investigated. The clinical and laboratory data of the patients were collected, the prognosis of patients diagnosed with CRO infection in day 30 was followed up, and the risk factors of prognosis were analyzed. The clinical significance of Carbapenem-Resistant Enterobacteriaceae (CRE) active screening was further evaluated in the CRE subgroup. Results: Among the total of 181 CRO isolates, 47.2% were CRE, 37.0% were Pseudomonas aeruginosa, and 32.6% were Klebsiella pneumoniae, which were highly resistant to carbapenem and had high MIC value, 76.8% (139/181) of CRO were MIC of imipenem resistance≥16 μg/ml. The main sources of isolates were blood and sputum. The 30-day all-cause mortality rates of patients with CRO or CRE infection were (41.4±3.7) % and (44.7±5.4) %, respectively. The COX multivariate regression analysis showed that the level of procalcitonin >0.2 ng/ml and the MIC value of imipenem resistance ≥ 16 μg/ml were independent risk factors for 30-day mortality of CRO infected patients. The CRE subgroup analysis showed that MIC value of imipenem resistance ≥16 μg/ml were independent risk factors for 30-day mortality of CRE infected patients. The 30-day cumulative survival rate of patients with CRE active screening was higher than the patients without CRE active screening [ (68.0±9.3) % vs (50.0±6.5) %, P =0.21]. Conclusion: The high MIC value of imipenem resistance isolates seriously affects the prognosis of patients with CRO infection in the hematology department, and the mortality rate was high. CRE active screening is expected for early prevention, early diagnosis, and early treatment for high-risk patients.

Published
2021
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results