Xiangyu Luo

Institute of Physics

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Xingjiang Zhou

Chinese Academy of Sciences

Zuyan Xu

Technical Institute of Physics and Chemistry

Qinjun Peng

Chinese Academy of Sciences

Fengfeng Zhang

Tengzhou Central People's Hospital

Shenjin Zhang

Technical Institute of Physics and Chemistry

Qiang Gao

Institute of Physics

C. T. Lin

Max Planck Institute for Solid State Research

Lin Zhao

University of Chinese Academy of Sciences

Genda Gu

Brookhaven National Laboratory

Chaohui Yin

Institute of Physics

Cooperative Institutions

Chinese Academy of Sciences

105

Institute of Physics

University of Chinese Academy of Sciences

National Laboratory for Superconductivity

University of Science and Technology of China

Chongqing University

Czech Academy of Sciences, Institute of Physics

Hefei National Center for Physical Sciences at Nanoscale

Songshan Lake Materials Laboratory

Tsinghua University

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High-efficiency grating coupler based on fast directional optimization and robust layout strategy in 130 nm CMOS process

Optics Letters (2022)

Xiangyu Luo Guangcan Mi Yanbo Li Tao Chu

We experimentally demonstrated a high-efficiency grating coupler by combining an interleaved etch and apodized structure for fiber-to-chip coupling. The grating coupler was optimized using the fast directional optimization method to achieve apodization. The grating coupler utilized a layout strategy involving an extended mask to avoid alignment errors for a multi-etch structure. The coupling efficiency was measured to be -2.2 dB at a wavelength of 1549 nm with a 3 dB bandwidth of 47 nm. The grating coupler, having no gold reflector, subwavelength index matching structure, or additional material layers, was fabricated using a commercial silicon photonics process with a minimum feature size of 140 nm. This grating coupler design provides a robust and effective coupling scheme and the proposed method can be employed to adopt the design in accordance with standard foundry design rules.

Apodization

10.1364/ol.452054

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Citations (15)

Vector Control Technology of Five‐Phase Induction Motor without Speed Sensor Based on Speed‐Adaptive Full‐Order Observer

IEEJ Transactions on Electrical and Electronic Engineering (2023)

Xiangyu Luo Jinghong Zhao Yiyong Xiong Rongtao Zeng

The five‐phase induction motor, being the most elementary form of multiphase induction motors, boasts low noise, low torque fluctuations, and high load‐bearing capacity, and is hence suitably employed in domains where high power and reliability are required. In light of the susceptibility of the speed encoder to interference from external environments, this paper proposes a sensorless vector control technique for the five‐phase induction motor based on a speed‐adaptive full‐order observer. The proposed approach first employs the nearest four‐vector space vector pulse width modulation (NFV‐SVPWM) as the modulation technique for the five‐phase inverter, in order to provide a constant switching frequency and low harmonic losses. Subsequently, the expression for the speed‐adaptive full‐order observer is constructed based on the mathematical model of the fundamental space of the five‐phase induction motor, and the expression for the adaptive speed law is deduced using the Lyapunov function. Additionally, the bilinear transformation method is utilized as the discretization technique for the full‐order observer during the process of digital implementation, in order to achieve higher discrete accuracy. Finally, an experimental study involving a 4.5 kW five‐phase induction motor was conducted to validate the accuracy and effectiveness of the proposed method. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Observer (physics)

Space vector modulation

Electronic speed control

10.1002/tee.23904

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The origin of superconductivity in nominally ‘undoped’ T′-La_2−xY_xCuO₄ films

Superconductor Science and Technology (2008)

Li Zhao Ronghua Liu Gang Wu Guoyu Wang Tianmin Wu

We have systematically studied the transport properties of the La$_{2-x}$Y$_{x}$CuO$_{4}$(LYCO) films of T'-phase ($0.05\leq x \leq 0.30$). In this nominally "undoped" system, superconductivity was acquired in certain Y doping range ($0.10\leq x \leq 0.20$). Measurements of resistivity, Hall coefficients in normal states and resistive critical field ($H^\rho_{c2}$)in superconducting states of the T'-LYCO films show the similar behavior as the known Ce-doped n-type cuprate superconductors, indicating the intrinsic electron-doping nature. The charge carriers are induced by oxygen deficiency. Non-superconducting Y-doped Pr- or Nd-based T'-phase cuprate films were also investigated for comparison, suggesting the crucial role of the radii of A-site cations in the origin of superconductivity in the nominally "undoped" cuptates. Based on a reasonable scenario in the microscopic reduction process, we put forward a self-consistent interpretation of these experimental observations.

10.1088/0953-2048/21/6/065005

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Ubiquitous coexisting electron-mode couplings in high-temperature cuprate superconductors

Proceedings of the National Academy of Sciences (2023)

Hongtao Yan Jin Mo Bok Jun-Feng He Wentao Zhang Qiang Gao

In conventional superconductors, electron-phonon coupling plays a dominant role in generating superconductivity. In high-temperature cuprate superconductors, the existence of electron coupling with phonons and other boson modes and its role in producing high-temperature superconductivity remain unclear. The evidence of electron-boson coupling mainly comes from angle-resolved photoemission (ARPES) observations of ∼ 70-meV nodal dispersion kink and ∼ 40-meV antinodal kink. However, the reported results are sporadic and the nature of the involved bosons is still under debate. Here we report findings of ubiquitous two coexisting electron-mode couplings in cuprate superconductors. By taking ultrahigh-resolution laser-based ARPES measurements, we found that the electrons are coupled simultaneously with two sharp modes at ∼ 70meV and ∼ 40meV in different superconductors with different dopings, over the entire momentum space and at different temperatures above and below the superconducting transition temperature. These observations favor phonons as the origin of the modes coupled with electrons and the observed electron-mode couplings are unusual because the associated energy scales do not exhibit an obvious energy shift across the superconducting transition. We further find that the well-known “peak-dip-hump” structure, which has long been considered a hallmark of superconductivity, is also omnipresent and consists of “peak-double dip-double hump” finer structures that originate from electron coupling with two sharp modes. These results provide a unified picture for the ∼ 70-meV and ∼ 40-meV energy scales and their evolutions with momentum, doping and temperature. They provide key information to understand the origin of these energy scales and their role in generating anomalous normal state and high-temperature superconductivity.

10.1073/pnas.2219491120

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Multi-objective optimum design of five-phase squirrel cage induction motor by differential evolution algorithm

Energy Reports (2022)

Hansi Chen Jinghong Zhao Hanming Wang Qingfei Zhang Xiangyu Luo

Compared with the traditional induction motors, five-phase squirrel cage induction motor (FSCIM) have the advantages of lower torque ripple and single-phase power, flexible control strategy, higher power density and fault-tolerant operation, which has been widely applied on electrical vehicles, rail transit, underwater vehicles and so on. This paper presents an analytical design optimization method based on the coupling of electromagnetic equivalent circuit (EEC) and differential evolution algorithm (DEA). Furthermore, the difference between three and five-phase winding on harmonic specific leakage permeance is investigated in detail. The nonlinear and oeolotropic influences of design geometrical parameters (slots openings, main dimension ratio, yoke height, airgap length, etc.) on the performances of the basic FSCIM model are evaluated with analytical model. For more accurate results, the harmonic characteristics of five-phase winding structure, iron core saturation, rotor slot skew width, stator end winding, slot leakage inductance and stator and rotor slot structure are considered. Meanwhile, the efficiency, power factor, maximum torque, slot fill factor and material consumption of FSCIM are calculated as the comprehensive objective function. The transient finite element analysis (TFEA) and experimental test verify the accuracy of the proposed optimum model. In addition, the feasibility of the multi objective optimization design scheme provided by the analytical model is verified by TFEA.

Leakage inductance

Torque ripple

Permeance

Squirrel-cage rotor

10.1016/j.egyr.2022.09.098

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Electron modulation strategy of heterogeneous Ni2P/FeP coupled with CeO2 for efficient overall water splitting

Fuel (2024)

Zefa Qin Yi Gan Dan Xiang Junchen Li Xinyue Li

Modulation (music)

10.1016/j.fuel.2024.133985

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Electronic Origin of High-Tc Maximization and Persistence in Trilayer Cuprate Superconductors

arXiv (Cornell University) (2022)

Xiangyu Luo Hao Chen Yinghao Li Qiang Gao Chaohui Yin

In high temperature cuprate superconductors, it was found that the superconducting transition temperature Tc depends on the number of CuO2 planes (n) in the structural unit and the maximum Tc is realized in the trilayer system (n=3). It was also found that the trilayer superconductors exhibit an unusual phase diagram that Tc keeps nearly constant in the overdoped region which is in strong contrast to the Tc decrease usually found in other cuprate superconductors. The electronic origin of the Tc maximization in the trilayer superconductors and its high Tc persistence in the overdoped region remains unclear. By taking high resolution laser-based angle resolved photoemission (ARPES) measurements, here we report our revelation of the microscopic origin of the unusual superconducting properties in the trilayer superconductors. For the first time we have observed the trilayer splitting in Bi2Sr2Ca2Cu3O10+d (Bi2223) superconductor. The observed Fermi surface, band structures, superconducting gap and the selective Bogoliubov band hybridizations can be well described by a three-layer interaction model. Quantitative information of the microscopic processes involving intra- and interlayer hoppings and pairings are extracted. The electronic origin of the maximum Tc in Bi2223 and the persistence of the high Tc in the overdoped region is revealed. These results provide key insights in understanding high Tc superconductivity and pave a way to further enhance Tc in the cuprate superconductors.

10.48550/arxiv.2210.06348

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Ubiquitous Coexisting Electron-Mode Couplings in High Temperature Cuprate Superconductors

arXiv (Cornell University) (2022)

Hongtao Yan Jin Mo Bok Junfeng He Wentao Zhang Qiang Gao

In conventional superconductors, the electron-phonon coupling plays a dominant role in pairing the electrons and generating superconductivity. In high temperature cuprate superconductors, the existence of the electron coupling with phonons and other boson modes and its role in producing high temperature superconductivity remain unclear. The evidence of the electron-boson coupling mainly comes from the angle-resolved photoemission (ARPES) observations of the ~70meV nodal dispersion kink and the ~40meV antinodal kink. However, the reported results are sporadic and the nature of the involved bosons are still under debate. Here we report new findings of ubiquitous two coexisting electron-mode couplings in cuprate superconductors. By taking ultra-high resolution laser-based ARPES measurements, combined with the improved second derivative analysis method, we discovered that the electrons are coupled simultaneously with two sharp phonon modes with energies of ~70meV and ~40meV in different superconductors with different doping levels, over the entire momentum space and at different temperatures above and below the superconducting transition temperature. The observed electron-phonon couplings are unusual because the associated energy scales do not exhibit an obvious change across the superconducting transition. We further find that the well-known "peak-dip-hump" structure, which has long been considered as a hallmark of superconductivity, is also omnipresent and consists of finer structures that originates from electron coupling with two sharp phonon modes. These comprehensive results provide a unified picture to reconcile all the reported observations and pinpoint the origin of the electron-mode couplings in cuprate superconductors. They provide key information to understand the role of the electron-phonon coupling in generating high temperature superconductivity.

10.48550/arxiv.2201.08108

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Potential usage of the magnetron-motion-free mode of one ion confined in a combined trap (vol 67, pg 235, 1998)

Mi Yan Xiangyu Luo X L Zhu

Cavity magnetron

Trap (plumbing)

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Spectroscopic evidence of bilayer splitting and strong interlayer pairing in the superconductor KCa2Fe4As4F2

Physical review. B./Physical review. B (2020)

Dingsong Wu Wenshan Hong Chenxiao Dong Xianxin Wu Qiangtao Sui

We report high-resolution laser-based angle-resolved photoemission spectroscopy measurements on a newly discovered iron-based superconductor, KCa2Fe4As4F2 (TC=33.5 K), which consists of stacking FeAs blocks with two FeAs layers separated by insulating Ca2F2 blocks. Bilayer splitting effect is observed for the first time in iron-based superconductors that gives rise to a total of five holelike Fermi surface sheets observed around the Brillouin zone center. Band structure calculations reproduce the observed bilayer splitting by identifying interlayer interorbital interaction between the two FeAs layers within one FeAs block. All the holelike pockets around the zone center exhibit Fermi surface-dependent and nodeless superconducting gap. The gap functions with short-range antiferromagnetic fluctuations are proposed and the gap symmetry can be well understood when the interlayer pairing is considered. The particularly strong interlayer pairing is observed for one of the bands. Our observations provide key information on the role of interlayer coupling and the interlayer pairing in generating superconductivity in iron-based superconductors.Received 1 February 2020Revised 6 May 2020Accepted 26 May 2020DOI:https://doi.org/10.1103/PhysRevB.101.224508©2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectronic structureSuperconducting gapSuperconducting order parameterSuperconductivityPhysical SystemsIron-based superconductorsSingle crystal materialsTechniquesAngle-resolved photoemission spectroscopyTight-binding modelCondensed Matter, Materials & Applied Physics

Brillouin zone

10.1103/physrevb.101.224508

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Citations (31)