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| 1 | Composite topological nodal lines penetrating the Brillouin zone in orthorhombic AgF_(2)显示文摘It has recently been found that nonsymmorphic symmetries can bring many exotic band crossings.Here,based on symmetry analysis,we predict that materials with time-reversal symmetry in the space group of Pbca(No.61)possess rich symmetry-enforced band crossings,including nodal surfaces,fourfold degenerate nodal lines and hourglass Dirac loops,which appear in triplets as ensured by the cyclic permutation symmetry.We take Pbca AgF_(2) as an example in real systems and studied its band structures with ab initio calculations.Specifically,in the absence of spin-orbit coupling(SOC),besides the above-mentioned band degeneracies,this system features a nodal chain and a nodal armillary sphere penetrating the Brillouin zone(BZ).While with SOC,we find a new configuration of the hourglass Dirac loop/chain with the feature traversing the BZ,which originates from the splitting of a Dirac loop confined in the BZ.Furthermore,guided by the bulk-surface correspondence,we calculated the surface states to explore these bulk nodal phenomena.The evolution of these interesting nodal phenomena traversing the BZ under two specific uniaxial strains is also discussed. | Dexi Shao Huaiqiang Wang Tong Chen Pengchao Lu Qinyan Gu Li Sheng Dingyu Xing Jian Sun | 2019 | npj Computational Materials2019，，1： | 0 |
| 2 | Long scan depth optical coherence tomography on imaging accommodation: impact of enhanced axial resolution, signal-to-noise ratio and speed显示文摘Background:Spectral domain optical coherence tomography(SD-OCT)was a useful tool to study accommodation in human eye,but the maximum image depth is limited due to the decreased signal-to-noise ratio(SNR).In this study,improving optical resolutions,speeds and the SNR were achieved by custom built SD-OCT,and the evaluation of the impact of the improvement during accommodation was investigated.Methods:Three systems with different spectrometer designs,including two Charge Coupled Device(CCD)cameras and one Complementary Metal-Oxide-Semiconductor Transistor(CMOS)camera,were tested.We measured the point spread functions of a mirror at different positions to obtain the axial resolution and the SNR of three OCT systems powered with a light source with a 50 nm bandwidth,centered at a wavelength of 840 nm.Two normal subjects,aged 26 and 47,respectively,and one 75-year-old patient with an intraocular lens implanted were imaged.Results:The results indicated that spectrometers using cameras with 4096 camera pixels optimized the axial resolutions,due to the use of the full spectrum provided by the light source.The CCD camera system with 4096 pixels had the highest SNR and the best image quality.The system with the CMOS camera with 4096 pixels had the highest speed but had a compromised SNR compared to the CCD camera with 4096 pixels.Conclusions:Using these three OCT systems,we imaged the anterior segment of the human eye before and after accommodation,which showed similar results among the different systems.The system using the CMOS camera with an ultra-long scan depth,high resolution and high scan speed exhibited the best overall performance and therefore was recommended for imaging real-time accommodation. | Yilei Shao Aizhu Tao Hong Jiang Meixiao Shen Dexi Zhu Fan Lu Carol LKarp Yufeng Ye Jianhua Wang | 2018 | Eye and Vision2018，5，1： | 0 |
| 3 | Quantum simulation of Hofstadter butterfly with synthetic gauge fields on two-dimensional superconducting-qubit lattices显示文摘Motivated by recent realizations of two-dimensional(2D)superconducting-qubit lattices,we propose a protocol to simulate Hofstadter butterfly with synthetic gauge fields in superconducting circuits.Based on the existing 2D superconducting-qubit lattices,we construct a generalized Hofstadter model on zigzag lattices,which has a fractal energy spectrum similar to the original Hofstadter butterfly.By periodically modulating the resonant frequencies of qubits,we engineer a synthetic gauge field to mimic the generalized Hofstadter Hamiltonian.A spectroscopic method is used to demonstrate the Hofstadter butterfly from the time evolutions of experimental observables.We numerically simulate the dynamics of the system with realistic parameters,and the results show a butterfly spectrum clearly.Our proposal provides a promising way to realize the Hofstadter butterfly on the latest 2D superconducting-qubit lattices and will stimulate the quantum simulation of novel properties induced by magnetic fields in superconducting circuits. | Wei Feng Dexi Shao Guo-Qiang Zhang Qi-Ping Su Jun-Xiang Zhang Chui-Ping Yang | 2023 | Frontiers of physics2023，18，6： | 0 |
| 4 | Large Spin Hall Conductivity and Excellent Hydrogen Evolution Reaction Activity in Unconventional PtTe1.75 Monolayer显示文摘Two-dimensional(2D)materials have gained lots of attention due to the potential applications.In this work,we propose that based on first-principles calculations,the(2×2)patterned PtTe_(2)monolayer with kagome lattice formed by the well-ordered Te vacancy(PtTe_(1.75))hosts large and tunable spin Hall conductivity(SHC)and excellent hydrogen evolution reaction(HER)activity.The unconventional nature relies on the A1@1b band representation of the highest valence band without spin–orbit coupling(SOC).The large SHC comes from the Rashba SOC in the noncentrosymmetric structure induced by the Te vacancy.Even though it has a metallic SOC band structure,theℤ_(2)invariant is well defined because of the existence of the direct bandgap and is computed to be nontrivial.The calculated SHC is as large as 1.25×10^(3)h/e(Ωcm)^(−1)at the Fermi level(EF).By tuning the chemical potential from EF−0.3 to EF+0.3 eV,it varies rapidly and monotonically from−1.2×10^(3)to 3.1×10^(3)h/e(Ωcm)^(−1)In addition,we also find that the Te vacancy in the patterned monolayer can induce excellent HER activity.Our results not only offer a new idea to search 2D materials with large SHC,i.e.,by introducing inversion–symmetry breaking vacancies in large SOC systems,but also provide a feasible system with tunable SHC(by applying gate voltage)and excellent HER activity. | Dexi Shao Junze Deng Haohao Sheng Ruihan Zhang Hongming Weng Zhong Fang Xing-Qiu Chen Yan Sun Zhijun Wang | 2023 | Research2023，，3： | 0 |
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