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Pressure tuning of the anomalous Hall effect in the kagome superconductor CsV_(3)Sb_(5)

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Chinese Physics B 2022年第1期31卷 31-36页

作者： Fang-Hang Yu Xi-Kai Wen Zhi-Gang Gui Tao Wu Zhenyu Wang Zi-Ji Xiang Jianjun Ying Xianhui Chen Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics and CAS Key Laboratory of Strongly-coupled Quantum Matter PhysicsUniversity of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in quantum Information and quantum Physics Hefei 230026China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093China

Controlling the anomalous Hall effect(AHE)inspires potential applications of quantum materials in the next generation of *** recently discovered quasi-2D kagome superconductor CsV_(3)Sb_(5) exhibits large AHE accompanying with the charge-density-wave(CDW)order which provides us an ideal platform to study the interplay among nontrivial band topology,CDW,and unconventional ***,we systematically investigated the pressure effect of the AHE in CsV_(3)Sb_(5).Our high-pressure transport measurements confirm the concurrence of AHE and CDW in the compressed CsV_(3)Sb_(5).Remarkably,distinct from the negative AHE at ambient pressure,a positive anomalous Hall resistivity sets in below 35 K with pressure around 0.75 GPa,which can be attributed to the Fermi surface reconstruction and/or Fermi energy shift in the new CDW phase under *** work indicates that the anomalous Hall effect in CsV_(3)Sb_(5) is tunable and highly related to the band structure.

关键词： anomalous Hall effect(AHE) charge-density-wave(CDW) kagome superconductor pressure effect

Melting of electronic/excitonic crystals in 2D semiconductor moirépatterns:A perspective from the Lindemann criterion

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Chinese Physics B 2023年第10期32卷 118-125页

作者：周纪勇唐剑炬俞弘毅 Guangdong Provincial Key Laboratory of quantum Metrology and Sensing&School of Physics and Astronomy Sun Yat-Sen University(Zhuhai Campus)Zhuhai 519082China State Key Laboratory of Optoelectronic Materials and technologies Sun Yat-Sen UniversityGuangzhou 510275China

Using the Lindemann criterion,we analyzed the quantum and thermal melting of electronic/excitonic crystals recently discovered in two-dimensional(2D)semiconductor moiré*** show that the finite 2D screening of the atomically thin material can suppress(enhance)the inter-site Coulomb(dipolar)interaction strength,thus inhibits(facilitates)the formation of the electronic(excitonic)***,a strong enough moiréconfinement is found to be essential for realizing the crystal phase with a wavelength near 10 nm or *** the calculated Lindemann ratio which quantifies the fluctuation of the site displacement,we estimate that the crystal will melt into a liquid above a critical temperature ranging from several tens Kelvin to above 100 K(depending on the system parameters).

关键词： moirépattern transition metal dichalcogenides electronic crystal excitonic crystal Lindemann criterion

Direct characteristic-function tomography of the quantum states of quantum fields

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Science China(Physics,Mechanics & Astronomy) 2023年第11期66卷 119-125页

作者： Zehua Tian Jiliang Jing Jiangfeng Du CAS Key Laboratory of Microscale Magnetic Resonance School of Physical SciencesUniversity of Science and Technology of ChinaHefei230026China CAS Center for Excellence in quantum Information and quantum Physics University of Science and Technology of ChinaHefei230026China Department of Physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Educationand Synergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha410081China Hefei National Laboratory University of Science and Technology of ChinaHefei230088China School of Physics Zhejiang UniversityHangzhou310027China

Herein,we propose a novel strategy for implementing a direct readout of the symmetric characteristic function of the quantum states of quantum fields without the involvement of idealized measurements,an aspect that has always been deemed ill-defined in quantum field *** proposed scheme relies on the quantum control and measurements of an auxiliary qubit locally coupled to the quantum *** mapping the expectation values of both the real and imaginary parts of the field displacement operator to the qubit states,the qubit's readout provides complete information regarding the symmetric characteristic *** characterize our technique by applying it to the Kubo-Martin-Schwinger(thermal)and squeezed states of a quantum scalar *** addition,we have discussed general applications of this approach to analogue-gravity systems,such as Bose-Einstein condensates,within the scope of state-of-the-art experimental *** proposed strategy may serve as an essential in understanding and optimizing the control of quantum fields for relativistic quantum information applications,particularly in exploring the interplay between gravity and quantum,for example,the relation to locality,causality,and information.

关键词： characteristic-function tomography quantum fields Ramsey interferometry analogue gravity

Optoelectronic properties of bottom gate-defined in-plane monolayer WSe_2 p–n junction

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Chinese Physics B 2018年第8期27卷 476-481页

作者： Di Liu Xiao-Zhuo Qi Takashi Taniguchi Xi-Feng Ren Guo-Ping Guo Key Laboratory of quantum Information University of Science and Technology of ChinaChinese Academy of SciencesHefei 230026China Synergetic Innovation Center of quantum Information&quantum Physics University of Science and Technology of ChinaHefei 230026China National Institute for Materials Science Namiki 1-1Ibaraki 305-0044Japan

Monolayer transition-metal dichalcogenides （TMDs） are considered to be fantastic building blocks for a wide variety of optical and optoelectronic devices such as sensors, photodetectors, and quantum emitters, owing to their direct band gap, transparency, and mechanical flexibility. The core element of many conventional electronic and optoelectronic devices is the p-n junction, in which the p- and n-types of the semiconductor are formed by chemical doping in different regions. Here, we report a series of optoelectronic studies on a monolayer WSe2 in-plane p-n photodetector, demonstrating a low- power dissipation by showing an ambipolar behavior with a reduced threshold voltage by a factor of two compared with the previous results on a lateral electrostatically doped WSe2 p-n junction. The fabrication of the device is based on a polycarbonates （PC） transfer technique and hence no electron-beam exposure induced damage to the monolayer WSe2 is expected. Upon optical excitation, the photodetector demonstrates a photoresponsivity of 0.12 mA.W-1 and a maximum external quantum efficiency of 0.03%. Our study provides an alternative platform for a flexible and transparent two- dimensional photodetector, from which we expect to further promote the development of next-generation optoelectronic devices.

关键词： WSe2, photodetector transfer technique p-n junction

Distributed phase-matching measurement for dynamic strain and temperature sensing based on stimulated Brillouin scattering enhanced four-wave mixing

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Photonics Research 2024年第1期12卷 141-153页

作者： YUAN WANG PEDRO TOVAR JUNTONG YANG LIANG CHEN XIAOYI BAO Nexus for quantum technologies University of OttawaOttawaOntario K1N 6N5Canada

A Brillouin dynamic grating(BDG) can be used for distributed birefringence measurement in optical fibers,offering high sensitivity and spatial resolution for sensing ***,it is quite a challenge to simultaneously achieve dynamic measurements with both high accuracy and high spatial *** this work,we propose a sensing mechanism to achieve distributed phase-matching measurement using a chirped pulse as a probe *** BDG reflection,the peak reflection corresponds to the highest four-wave mixing(FWM) conversion efficiency,and it requires the Brillouin frequency in the fast and slow axes to be equal,which is called the phase-matching *** condition changes at different fiber positions,which requires a range of frequency injection for the probe *** proposed method uses a chirped pulse as a probe wave to cover this frequency range associated with distributed birefringence *** allows us to detect distributed phase matching for birefringence changes that are introduced by temperature and strain *** to the single shot and direct time delay measurement capability,the acquisition rate in our system is only limited by the fiber ***,unlike conventional BDG spectrum recovery-based systems,the spatial resolution here is determined by both the frequency chirping rate of the probe pulse and the birefringence profile of the *** the experiments,an acquisition rate of 1 k Hz(up to fiber length limits) and a spatial resolution of 10 cm using a 20 ns probe pulse width are *** minimum detectable temperature and strain variation are 5.6 mK and 0.37 με along a 2 km long polarization-maintaining fiber(PMF).

关键词： fiber scattering polarization

Experimental demonstrations of high-Q superconducting coplanar waveguide resonators

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Chinese Science Bulletin 2013年第20期58卷 2413-2417页

作者： LI HaiJie WANG YiWen WEI LianFu ZHOU PinJia WEI Qiang CAO ChunHai FANG YuRong YU Yang WU PeiHeng quantum Optoelectronics Laboratory Southwest Jiaotong University State Key Laboratory of Optoelectronic Materials and technologies School of Physics and Engineering Sun Yat-sen University Research Institute of Superconductor Electronics Nanjing University

We successfully designed and fabricated an absorption-type of superconducting coplanar waveguide (CPW) resonators. The resonators are made from a niobium film (about 160 nm thick) on a high-resistance Si substrate, and each resonator is fabricated as a meandered quarter-wavelength transmission line (one end is short to the ground and another end is capacitively coupled to a through feedline). With a vector network analyzer we measured the transmissions of the applied microwave through the resonators at ultra-low temperature. The obtained loaded quality factors are significantly high, i.e. up to ～10 6 . When the temperature increases slowly from the base temperature (20 mK), the resonance frequencies of the resonators are blue shifted and the quality factors are lowered slightly. In principle, this type of device can integrate a series of CPW resonators with a common feedline, making it a promising candidate as the data bus for coupling distant solid-state qubits and the sensitive detector of single photons.

关键词：共面波导谐振器实验演示超导高Q值矢量网络分析仪单光子探测器质量因素

Production of ^(87)Rb Bose-Einstein Condensate in an Asymmetric Crossed Optical Dipole Trap

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Chinese Physics Letters 2021年第10期38卷 12-16页

作者： Zhu Ma Chengyin Han Xunda Jiang Ruihuan Fang Yuxiang Qiu Minhua Zhao Jiahao Huang Bo Lu Chaohong Lee Guangdong Provincial Key Laboratory of quantum Metrology and Sensing&School of Physics and Astronomy Sun Yat-Sen University(Zhuhai Campus)State Key Laboratory of Optoelectronic Materials and TechnologiesSun Yat-Sen University(Guangzhou Campus)Zhuhai 519082China State Key Laboratory of Optoelectronic Materials and technologies Sun Yat-Sen University(Guangzhou Campus)Guangzhou 510275China

We report the production of ^(87)Rb Bose–Einstein condensate in an asymmetric crossed optical dipole trap(ACODT)without the need of an additional dimple *** our experiment,the ACODT is formed by two laser beams with different radii to achieve efficient capture and rapid evaporation of laser cooled *** to the cooling procedure in a magnetic trap,the atoms are firstly laser cooled and then directly loaded into an ACODT without the pre-evaporative cooling *** order to determine the optimal parameters for evaporation cooling,we optimize the power ratio of the two beams and the evaporation time to maximize the final atom number left in the *** loading about 6×10^(5) laser cooled atoms in the ACODT,we obtain a pure Bose–Einstein condensate with about 1.4×10^(4) atoms after 19 s ***,we demonstrate that the fringe-type noises in optical density distributions can be reduced via principal component analysis,which correspondingly improves the reliability of temperature measurement.

关键词： measurement Einstein Bose

An improved differential evolution algorithm for learning high-fidelity quantum controls

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Science Bulletin 2019年第19期64卷 1402-1408页

作者： Xiaodong Yang Jun Li Xinhua Peng CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics University of Science and Technology of ChinaHefei230026China Shenzhen Institute for quantum Science and Engineering and Department of Physics Southern University of Science and TechnologyShenzhen518055China Center for quantum Computing Peng Cheng LaboratoryShenzhen518055China Shenzhen Key Laboratory of quantum Science and Engineering Southern University of Science and TechnologyShenzhen518055China Synergetic Innovation Centre of quantum Information&quantum Physics University of Science and Technology of ChinaHefei230026China

Precisely and efficiently designing control pulses for the preparation of quantum states and quantum gates are the fundamental tasks for quantum ***-based optimal control methods are the routine to design such ***,the gradient information is often difficult to calculate or measure,especially when the system is not well calibrated or in the presence of various ***-free evolutionary algorithm is an alternative choice to accomplish this task but usually with ***,we design an efficient mutation rule by using the information of the current and the former individuals *** leads to our improved differential evolution algorithm,called da *** demonstrate its performance,we numerically benchmark the pulse optimization for quantum states and quantum gates preparations on small-scale NMR *** numerical comparisons with conventional differential evolution algorithms show that da DE has great advantages on the convergence speed and robustness to several uncertainties including pulse imperfections and measurement errors.

关键词： Control pulses searching Differential evolution quantum states and gates preparation Pulse imperfections Random measurement errors

Orbital angular momentum complex spectrum analyzer for vortex light based on the rotational Doppler effect

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Light(Science & Applications) 2016年第1期5卷 88-95页

作者： Hai-Long Zhou Dong-Zhi Fu Jian-Ji Dong Pei Zhang Dong-Xu Chen Xin-Lun Cai Fu-Li Li Xin-Liang Zhang Wuhan National Laboratory for Optoelectronics School of Optical and Electronic InformationHuazhong University of Science and TechnologyWuhan 430074China Key Laboratory for quantum Information and quantum Optoelectronic Devices Shaanxi ProvinceDepartment of Applied PhysicsXi’an Jiaotong UniversityXi’an 710049China State Key Laboratory of Optoelectronic Materials and technologies and School of Physics and Engineering Sun Yatsen UniversityGuangzhou 510275China

The ability to measure the orbital angular momentum(OAM)distribution of vortex light is essential for OAM *** there have been many studies on the measurement of OAM modes,it is difficult to quantitatively and instantaneously measure the power distribution among different OAM modes,let alone measure the phase distribution among *** this work,we propose an OAM complex spectrum analyzer that enables simultaneous measurements of the power and phase distributions of OAM modes by employing the rotational Doppler *** original OAM mode distribution is mapped to an electrical spectrum of beat signals using a *** power and phase distributions of superimposed OAM beams are successfully retrieved by analyzing the electrical *** also extend the measurement technique to other spatial modes,such as linear polarization *** results represent a new landmark in spatial mode analysis and show great potential for applications in OAM-based systems and optical communication systems with mode-division multiplexing.

关键词： mode analysis orbital angular momentum rotational Doppler effect