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Quantized anomalous Hall resistivity achieved in molecular beam epitaxy-grown Mn Bi2Te4 thin films

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National science Review 2024年第2期11卷 24-32页

作者： Yunhe Bai Yuanzhao Li Jianli Luan Ruixuan Liu Wenyu Song Yang Chen Peng-Fei Ji Qinghua Zhang Fanqi Meng Bingbing Tong Lin Li Yuying Jiang Zongwei Gao Lin Gu Jinsong Zhang Yayu Wang Qi-Kun Xue Ke He Yang Feng Xiao Feng State Key Laboratory of Low Dimensional quantum Physics Department of Physics Tsinghua University Institute of Physics Chinese Academy of Sciences School of Materials science and Engineering Tsinghua University Beijing Academy of quantum Information sciences Frontier science Center for quantum Information Hefei National Laboratory Southern University of science and Technology

The intrinsic magnetic topological insulator MnBi2Te4provides a feasible pathway to the high-temperature quantum anomalous Hall（QAH） effect as well as various novel topological quantum phases. Although quantized transport properties have been observed in exfoliated MnBi2Te4thin flakes, it remains a big challenge to achieve molecular beam epitaxy（MBE）-grown MnBi2Te4thin films even close to the quantized regime. In this work, we report the realization of quantized anomalous Hall resistivity in MBE-grown MnBi2Te4thin films with the chemical potential tuned by both controlled in situ oxygen exposure and top gating. We find that elongated post-annealing obviously elevates the temperature to achieve quantization of the Hall resistivity, but also increases the residual longitudinal resistivity, indicating a picture of high-quality QAH puddles weakly coupled by tunnel barriers. These results help to clarify the puzzles in previous experimental studies on MnBi2Te4and to find a way out of the big difficulty in obtaining MnBi2Te4samples showing quantized transport properties.

关键词： intrinsic magnetic topological insulator quantized anomalous Hall resistivity molecular beam epitaxy quantized transport property

Cryogenic transmission electron microscopy on beam-sensitive materials and quantum science

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Chinese Physics B 2024年第8期33卷 9-29页

作者：王刚林君浩 Department of Physics and Shenzhen Key Laboratory of Advanced quantum Functional Materials and Devices Southern University of Science and TechnologyShenzhen 518055China quantum science Center of Guangdong–Hong Kong–Macao Greater Bay Area(Guangdong) Shenzhen 518045China

Transmission electron microscopy(TEM)offers unparalleled atomic-resolution imaging of complex materials and heterogeneous ***,high-energy imaging electrons can induce structural damage,posing a challenge for electron-beam-sensitive *** TEM(Cryo-TEM)has revolutionized structural biology,enabling the visualization of biomolecules in their near-native states at unprecedented *** low electron dose imaging and stable cryogenic environment in Cryo-TEM are now being harnessed for the investigation of electron-beam-sensitive materials and low-temperature quantum ***,we present a systematic review of the interaction mechanisms between imaging electrons and atomic structures,illustrating the electron beam-induced damage and the mitigating role of *** review then explores the advancements in low-dose Cryo-TEM imaging for elucidating the structures of organic-based ***,we showcase the application of Cryo-TEM in the study of strongly correlated quantum materials,including the detection of charge order and novel topological spin ***,we discuss the future prospects of Cryo-TEM,emphasizing its transformative potential in unraveling the complexities of materials and phenomena across diverse scientific disciplines.

关键词： cryogenic TEM low dose imaging quantum materials

Bimodal growth of Fe islands on graphene

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Chinese Physics B 2024年第6期33卷 553-557页

作者：顾翊晟俞俏滟刘荡孙蓟策席瑞骏陈星森薛莎莎章毅杜宪宁旭辉杨浩管丹丹刘晓雪刘亮李耀义王世勇刘灿华郑浩贾金锋 Key Laboratory of Artificial Structures and quantum Control TD Lee InstituteShenyang National Laboratory for Materials ScienceSchool of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Department of Physics Southern University of Science and TechnologyShenzhen 518055China quantum science Center of Guangdong-Hong Kong-Macao Greater Bay Area(Guangdong) Shenzhen 518045China

Magnetic metals deposited on graphene hold the key to applications in spintronics. Here, we present the results of Fe islands grown on graphene/Si C(0001) by molecular beam epitaxy, which are investigated by scanning tunneling microscopy. The two types of islands distinguished by flat or round tops are revealed, indicating bimodal growth of Fe. The atomic structures on the top surfaces of flat islands are also clearly resolved. Our results may improve the understanding of the mechanisms of metals deposited on graphene and pave the way for future spintronic applications of Fe/graphene systems.

关键词： graphene magnetism molecular beam epitaxy scanning tunneling microscopy

High-resolution recognition of FOAM modes via an improved EfficientNet V2 based convolutional neural network

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Frontiers of physics 2024年第3期19卷 175-183页

作者： Youzhi Shi Zuhai Ma Hongyu Chen Yougang Ke Yu Chen Xinxing Zhou International Collaborative Laboratory of 2D Materials for Optoelectronics science and Technology Institute of Microscale OptoelectronicsShenzhen UniversityShenzhen 518060China Key Laboratory of Low-Dimensional quantum Structures and quantum Control of Ministry of Education Synergetic Innovation Center for Quantum Effects and ApplicationsSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China Key Laboratory of Hunan Province on Information Photonics and Freespace Optical Communications School of Information Science and EngineeringHunan Institute of Science and TechnologyYueyang 414006China

Vortex beam with fractional orbital angular momentum (FOAM) is the excellent candidate for improving the capacity of free-space optical (FSO) communication system due to its infinite modes. Therefore, the recognition of FOAM modes with higher resolution is always of great concern. In this work, through an improved EfficientNetV2 based convolutional neural network (CNN), we experimentally achieve the implementation of the recognition of FOAM modes with a resolution as high as 0.001. To the best of our knowledge, it is the first time this high resolution has been achieved. Under the strong atmospheric turbulence (AT) (C_(n)^(2)=10^(-15)m^(-2/3)), the recognition accuracy of FOAM modes at 0.1 and 0.01 resolution with our model is up to 99.12% and 92.24% for a long transmission distance of 2000 m. Even for the resolution at 0.001, the recognition accuracy can still remain at 78.77%. This work provides an effective method for the recognition of FOAM modes, which may largely improve the channel capacity of the free-space optical communication.

关键词： OAM free-space optical communication deep learning convolutional neural network

Microscopic growth mechanism and edge states of monolayer 1T'-MoTe2

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Chinese Physics B 2024年第4期33卷 474-480页

作者：赵海鹏刘隐杨胜国林陈昉陈明星 Kai Braun 罗心仪李思宇潘安练王笑 Key Laboratory for Micro-Nano Physics and Technology of Hunan Province School of Physics and ElectronicsCollege of Materials Science and Engineering Hunan University Key Laboratory of Low-Dimensional quantum Structures and quantum Control of Ministry of Education Synergetic Innovation Centre for Quantum Effects and Applications (SICQEA) Hunan Normal University State Key Laboratory of Powder Metallurgy Central South University Institute of Physical and Theoretical Chemistry and LISA+ University of Tübingen

Transition metal ditellurides（TMTDs） have versatile physical properties,including non-trivial topology,Weyl semimetal states and unique spin *** growth of high-quality and large-scale monolayer TMTDs with preferred crystal phases is crucial for their ***,we demonstrate the epitaxial growth of 1T'-MoTe2on Au（111）and graphitized silicon carbide（Gr/SiC） by molecular beam epitaxy（MBE）.We investigate the morphology of the grown1T'-MoTe2at the atomic level by scanning tunnelling microscopy（STM） and reveal the corresponding microscopic growth *** is found that the unique ordered Te structures preferentially deposited on Au（111） regulate the growth of monolayer single crystal 1T'-MoTe2,while the Mo clusters were preferentially deposited on the Gr/SiC substrate,which impedes the ordered growth of monolayer *** confirm that the size of single crystal 1T'-MoTe2grown on Au（111）is nearly two orders of magnitude larger than that on Gr/*** scanning tunnelling spectroscopy（STS）,we observe that the STS spectrum of the monolayer 1T'-MoTe2nano-island at the edge is different from that at the interior,which exhibits enhanced conductivity.

关键词： 1T′-MoTe2 microscopic growth mechanism scanning tunneling microscopy/spectroscopy (STM/S) transition metal ditellurides

Electro-optic 3D snapshot of a laser wakefield accelerated kilo-ampere electron bunch

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Light(science & Applications) 2024年第5期13卷 823-834页

作者： Kai Huang Zhan Jin Nobuhiko Nakanii Tomonao Hosokai Masaki Kando Kansai Institute for Photon science(KPSI) National Institutes for Quantum Science and Technology(QST)KyotoJapan. Laser Accelerator R&D Innovative Light Sources DivisionRIKEN SPring-8 CenterHyogoJapan. SANKEN Osaka UniversityOsakaJapan

Laser wakefield acceleration,as an advanced accelerator concept,has attracted great attentions for its ultrahigh acceleration gradient and the capability to produce high brightness electron *** three-dimensional(3D)density serves as an evaluation metric for the particle bunch quality and is intrinsically related to the applications of an *** its significance,this parameter has not been experimentally measured in the investigation of laser wakefield *** report on an electro-optic 3D snapshot of a laser wakefield electron bunch at a position outside the *** 3D shape of the electron bunch was detected by simultaneously performing optical transition radiation imaging and electro-optic *** 3D structures to a few micrometer levels were reconstructed using a genetic *** electron bunch possessed a transverse size of less than 30 *** current profile shows a multi-peak *** main peak had a duration of1 *** maximum electron 3D number density was~9×10^(21)m^(-3).This research demonstrates a feasible way of 3D density monitoring on femtosecond kilo-ampere electron bunches,at any position of a beam transport line for relevant applications.

关键词： laser acceleration field

Distribution of polarization squeezed light through a 20 km fiber channel

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science China(Information sciences) 2024年第5期67卷 343-344页

作者： Chao LI Siyu REN Yanru YAN Yalin LI Meihong WANG Xiaolong SU State Key Laboratory of quantum Optics and quantum Optics Devices Institute of Opto-Electronics Shanxi University Collaborative Innovation Center of Extreme Optics Shanxi University

Polarization squeezed light plays a key role in quantum memory by transferring quantum information between atoms and photons [1], and has potential applications in quantum precision measurement [2]. For polarization squeezed light, the quantum variance of at least one Stokes operator is smaller than that of the coherent *** with the quadrature squeezed state, polarization squeezed light has the following advantages: one is that it is a bright beam, and the other is that it can be measured directly without using a local oscillator.

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Spatial quantum coherent modulation with perfect hybrid vector vortex beam based on atomic medium

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Chinese Physics B 2024年第2期33卷 360-364页

作者：马燕杨欣常虹杨鑫琪曹明涛张晓斐高宏董瑞芳张首刚 Key Laboratory of Time Reference and Applications National Time Service CenterChinese Academy of SciencesXi’an 710600China School of Astronomy and Space science University of Chinese Academy of SciencesBeijing 100049China Ministry of Education Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter Shaanxi Key Laboratory of Quantum Information and Quantum Optoelectronic DevicesSchool of ScienceXi’an Jiaotong UniversityXi’an 710049China Department of Physics Shaanxi University of Science and TechnologyXi’an 710021China Hefei National Laboratory Hefei 230088China

The perfect hybrid vector vortex beam(PHVVB)with helical phase wavefront structure has aroused significant concern in recent years,as its beam waist does not expand with the topological charge(TC).In this work,we investigate the spatial quantum coherent modulation effect with PHVVB based on the atomic medium,and we observe the absorption characteristic of the PHVVB with different TCs under variant magnetic *** find that the transmission spectrum linewidth of PHVVB can be effectively maintained regardless of the ***,the width of transmission peaks increases slightly as the beam size expands in hot atomic *** distinctive quantum coherence phenomenon,demonstrated by the interaction of an atomic medium with a hybrid vector-structured beam,might be anticipated to open up new opportunities for quantum coherence modulation and accurate magnetic field measurement.

关键词： perfect hybrid vector vortex beam topological charge quantum coherence optical manipulation

Optimal preparation of Bose and Fermi atomic gas mixtures of ^(87)Rb and ^(40)K in a crossed optical dipole trap

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Chinese Physics B 2024年第6期33卷 356-361页

作者：丁培波单标赵宇航杨雅婧陈良超孟增明王鹏军黄良辉 State Key Laboratory of quantum Optics and quantum Optics Devices Institute of Opto-electronicsCollaborative Innovation Center of Extreme OpticsShanxi UniversityTaiyuan 030006China Hefei National Laboratory Hefei 230000China

We report on the optimal production of the Bose and Fermi mixtures with ^(87) Rb and ^(40)K in a crossed optical dipole trap(ODT).We measure the atomic number and lifetime of the mixtures in combination of the spin state |F=9/2,m_(F)=9/2> of^(40)K and |1,1>of ^(87) Rb in the ODT,which is larger and longer compared with the combination of the spin state |9/2,9/2> of^(40)K and 12,2) of ^(87)Rb in the *** observe the atomic numbers of ^(87)Rb and ^(40)K shown in each stage of the sympathetic cooling process while gradually reducing the depth of the optical *** optimizing the relative loading time of atomic mixtures in the MOT,we obtain the large atomic number of ^(40)K(~6 ×10^(6)) or the mixtures of atoms with an equal number(~1.6 × 10^(6)) at the end of evaporative cooling in the *** experimentally investigate the evaporative cooling in an enlarged volume of the ODT via adding a third laser beam to the crossed ODT and found that more atoms(8 × 10^(6)) and higher degeneracy(T/T_(F)=0.25) of Fermi gases are *** ultracold atomic gas mixtures pave the way to explore phenomena such as few-body collisions and the Bose-Fermi Hubbard model,as well as for creating ground-state molecules of ^(87)Rb^(40)K.

关键词： optical dipole trap Bose and Fermi gas mixtures atomic lifetime