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Magnetic field imaging with radio-frequency optically pumped magnetometers [Invited]

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Chinese Optics Letters 2024年第6期22卷 38-45页

作者： Xiyu Liu Junlong Han Wei Xiao Teng Wu Xiang Peng Hong Guo School of Electronics Peking UniversityBeijing 100871China

High-sensitivity radio-frequency optically pumped magnetometers (RF-OPMs), working without cryogenic condition, play a critical role in magnetic field imaging(MFI) at low frequencies(e.g., 100 Hz to 1 MHz). We introduce the principle of operation and recent developments of RF-OPMs and focus on reviewing the MFI applications in magnetic induction tomography, ultralow-field magnetic resonance imaging, and magnetic particle imaging. For the applications of RF-OPMs, ranging from industrial monitoring to medical imaging and security screening, the unshielded and portable RF-OPMs(and RF-OPM array)techniques are still under the further development for detecting and scanning over the target object for accomplishing the final three-dimensional imaging, and thus extremely require the abilities of active compensation of the ambient magnetic field and sensor miniaturization in the future.

关键词： magnetic field imaging radio frequency optically pumped magnetometer

Regulating Anderson localization with structural defect disorder

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Chinese Physics B 2024年第10期33卷 102-107页

作者： Mouyang Cheng Haoxiang Chen Ji Chen School of Physics Peking UniversityBeijing 100871China Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials Peking UniversityBeijing 100871China Frontiers Science Center for Nano-Optoelectronics Peking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter Beijing 100871China

Localization due to disorder has been one of the most intriguing theoretical concepts that evolved in condensed matter ***,we expand the theory of localization by considering two types of disorders at the same time,namely,the original Anderson’s disorder and the structural defect disorder,which has been suggested to be a key component in recently discovered two-dimensional amorphous *** increasing the degree of both disorders could induce localization of wavefunction in real space,we find that a small degree of structural defect disorder can significantly enhance the *** the degree of structural defect disorder increases,localized states quickly appear within the extended phase to enter a broad crossover region with mixed *** establish two-dimensional diagrams for the wavefunction localization and conductivity to highlight the interplay between the two types of *** theoretical model provides a comprehensive understanding of localization in two-dimensional amorphous materials and highlights the promising tunability of their transport properties.

关键词： Anderson localization structural defect disorder electronic transport properties

Magnetism and Superconductivity in the t–J Model of La_(3)Ni_(2)O_7 Under Multiband Gutzwiller Approximation

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Chinese Physics Letters 2024年第5期41卷 97-106页

作者：薛洁然王垡 International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter Beijing 100871China

The recent discovery of possible high temperature superconductivity in single crystals of La_(3)Ni_(2)O_(7) under pressure renews the interest in research on *** density functional theory calculations reveal that both d_(z^(2)) and d_(x^(2)-y^(2)) orbitals are active,which suggests a minimal two-orbital model to capture the low-energy physics of this *** this work,we study a bilayer two-orbital t–J model within multiband Gutzwiller approximation,and discuss the magnetism as well as the superconductivity over a wide range of the hole *** to the inter-orbital super-exchange process between d_(z^(2)) and d_(x^(2)-y^(2)) orbitals,the induced ferromagnetic coupling within layers competes with the conventional antiferromagnetic coupling,and leads to complicated hole doping dependence for the magnetic properties in the *** increasing hole doping,the system transfers to A-type antiferromagnetic state from the starting G-type antiferromagnetic(G-AFM)*** also find the inter-layer superconducting pairing of d_(x^(2)-y^(2)) orbitals dominates due to the large hopping parameter ofd_(z^(2)) along the vertical inter-layer bonds and significant Hund’s coupling between d_(z^(2)) and d_(x^(2)-y^(2)) ***,the G-AFM state and superconductivity state can coexist in the low hole doping *** take account of the pressure,we also analyze the impacts of inter-layer hopping amplitude on the system properties.

关键词： properties doping orbital

Dual-objective two-photon microscope for volumetric imaging of dense scattering biological samples by bidirectional excitation and collection

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Photonics Research 2024年第6期12卷 1351-1361页

作者： MUYUE ZHAI JING YU YANHUI HU HANG YU BEICHEN XIE YI YU DAWEI LI AIMIN WANG HEPING CHENG National Biomedical Imaging Center College of Future TechnologyPeking UniversityBeijing 100871China Research Unit of Mitochondria in Brain Diseases Chinese Academy of Medical SciencesPKU-Nanjing Institute of Translational MedicineNanjing 211500China beijing Transcend Vivoscope Biotech Beijing 100085China College of Engineering Peking UniversityBeijing 100871China Academy for Advanced Interdisciplinary Studies Peking UniversityBeijing 100871China Center for Quantitative Biology Peking UniversityBeijing 100871China School of Electronics Peking UniversityBeijing 100871China State Key Laboratory of Advanced Optical Communication System and Networks Peking UniversityBeijing 100871China

Full view observation throughout entire specimens over a prolonged period is crucial when exploring the physiological functions and system-level ***-photon microscopy(MPM)has been widely employed for such purposes owing to its deep penetration ***,the current MPM struggles with balancing the imaging depth and quality while avoiding photodamage for the exponential increasement of excitation power with the imaging ***,we present a dual-objective two-photon microscope(Duo-2P),characterized by bidirectional two-photon excitation and fluorescence collection,for long-duration volumetric imaging of dense scattering ***-2P effectively doubles the imaging depth,reduces the total excitation energy by an order of magnitude for samples with a thickness five times the scattering length,and enhances the signal-to-noise ratio up to 1.4 *** these advantages,we acquired volumetric images of a 380-μm suprachiasmatic nucleus slice for continuous 4-h recording at a rate of 1.67 s/volume,visualized the calcium activities over 4000 neurons,and uncovered their state-switching *** conclude that Duo-2P provides an elegant and powerful means to overcome the fundamental depth limit while mitigating photodamages for deep tissue volumetric imaging.

关键词： excitation overcome exponential

A historical overview of nano-optics:From near-field optics to plasmonics

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Chinese Physics B 2024年第5期33卷 134-145页

作者：邓妙怡朱星 Department of History of Science Technology and MedicineAcademy for Advanced Interdisciplinary StudiesPeking UniversityBeijing 100871China School of Physics Peking UniversityBeijing 100871China

Nano-optics is an emergent research field in physics that appeared in the 1980s,which deals with light–matter optical interactions at the nanometer *** early studies of nano-optics,the main concern focus is to obtain higher optical resolution over the diffraction *** researches of near-field imaging and spectroscopy based on scanning near-field optical microscopy(SNOM)are *** exploration of improving SNOM probe for near-field detection leads to the emergence of surface *** the sense of resolution and wider application,there has been a significant transition from seeking higher resolution microscopy to plasmonic near-field modulations in the nano-optics community during the nano-optic ***,studies of nano-optics prefer the investigation of plasmonics in different material *** this article,the history of the development of near-field optics is briefly *** difficulties of conventional SNOM to achieve higher resolution are *** an alternative solution,surface plasmons have shown the advantages of higher resolution,wider application,and flexible nano-optical modulation for new *** typical studies in different periods are introduced and characteristics of nano-optics in each stage are *** this way,the evolution progress from near-field optics to plasmonics of nano-optics research is *** future development of nano-optics is discussed then.

关键词： nano-optics near-field optics surface plasmon plasmonic modulation

Recent Developments on the H_(I)Gas of Low-Redshift Galaxies Seen by the 21 cm Emission Lines

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Chinese Physics Letters 2024年第10期41卷 152-165页

作者： Jing Wang Xuchen Lin Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China Department of Astronomy School of PhysicsPeking UniversityBeijing 100871China

As a major interstellar medium,the atomic neutral hydrogen(H I)plays an important role in the galaxy *** provides the ingredient for star formation,and sensitively traces the internal processes and external perturbations influencing the *** the beginning of many new radio telescopes and surveys,H_(I)may make a more significant contribution to the understanding of galaxies in the near *** review discusses the major development of the 21 cm emission-line H_(I)observations and studies in the past few years,including its scaling relations with other galaxy properties,its kinematics and structures,its role in environmental studies,and its constraints on hydrodynamical *** local-Universe H_(I)scaling relations of stellar-massselected samples extend smoothly to 10_(9)M⊙stellar mass,with a tentative evolution to the redshift of∼*** development of measurement techniques enables better estimations of H_(I)non-circular motion,dispersion,and thickness,and new observations revealed extended or extra-planar H_(I)structures,both helpfully constraining the gas accretion,stellar feedback,and star formation processes of galaxy evolution models.H_(I)is very useful for tracing the satellite evolution in dense environments,the studies of which would benefit from ongoing blind H_(I)*** simulations still cannot fully reproduce H_(I)gas properties,they help to understand the role of possible factors in regulating H_(I)properties.

关键词： evolution. galaxy stellar

A scheme to fix multiple solutions in amplitude analyses

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Chinese Physics C 2024年第5期48卷 8-22页

作者：高原宁荣天泽杨振伟张辰佳张艳席 School of Physics Peking UniversityBeijing 100871China

Decays of unstable heavy particles usually involve the coherent sum of several amplitudes,like in a multiple slit *** amplitude analysis techniques have been widely used to resolve these amplitudes for better understanding of the underlying *** special cases where two spin-1/2 particles and two(pseudo-)scalar particles are present in the process,multiple equivalent solutions are found owing to intrinsic symmetries in the summed probability density *** this study,the problem of multiple solutions is discussed,and a scheme to overcome this problem is proposed by fixing some free *** are generated to validate the strategy.A new approach to align the helicities of initial-and final-state particles in different decay chains is also introduced.

关键词： amplitude analysis multiple solutions helicity formalism

Collective flow and fluid behavior in p/d/^(3)He+Au collisions at√s_(NN)=200 GeV

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Chinese Physics C 2024年第10期48卷 185-192页

作者： Zeming Wu Baochi Fu Shujun Zhao Runsheng Liu Huichao Song School of Physics Peking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter Beijing 100871China Center for High Energy Physics Peking UniversityBeijing 100871China

By varying the intrinsic initial geometry,p/d/^(3)He+Au collisions at the Relativistic Heavy Ion Collider(RHIC)provide a unique opportunity to understand the collective behavior and probe possible sub-nucleon fluctuations in small *** this study,we employed the hybrid model under TRENTo initial conditions to study the collective flow and fluid behavior in p/d/^(3)He+Au *** fine-tuned parameters,iEBE-VISHNU can describe the v_(2)(pT) and v_(3)(pT) data from the PHENIX and STAR ***,for certain parameter sets with initial sub-nucleon fluctuations,the hydrodynamic simulations already go beyond their limits with an average Knudsen number clearly larger than *** calculations demonstrate that,for a meaningful evaluation of the fluid behavior in small systems,model simulations must also pay attention to the validity range of hydrodynamics.

关键词： heavy-ion collisions hydrodynamics collective flow

Threshold of climate extremes that impact vegetation productivity over the Tibetan Plateau

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Science China Earth Sciences 2024年第6期67卷 1967-1977页

作者： Zhenggang PIAO Xiangyi LI Hao XU Kai WANG Shuchang TANG Fei KAN Songbai HONG College of Urban and Environmental Sciences Peking UniversityBeijing 100871China

Vegetation growth is adversely impacted by multiple climate extremes related to the water and thermal stress over the Tibetan Plateau(TP).However,it remains unknown at which stress level these climate extremes can trigger the abrupt shifts of vegetation response to climate extremes and result in the maximum vegetation response across *** fill this knowledge gap,we combined the hydrometeorological data and the satellite-derived vegetation index to detect two critical thresholds that determine the response of vegetation productivity to droughts,high-temperature extremes,and low-temperature extremes,respectively,during *** results show that the response of vegetation productivity to droughts rapidly increases once crossing -1.41±0.6 standard deviation(σ)below the normal conditions of soil *** crossing-2.98σ±0.9σ,vegetation productivity is maximum damaged by ***-temperature extremes,which have the two thresholds of 1.34σ±0.4σand 2.31σ±0.4σover TP,are suggested to trigger the strong response of vegetation productivity at a milder stress level than low-temperature extremes(two thresholds:-1.44σ±0.5σand-2.53σ±0.8σ).Moreover,we found the compounded effects of soil moisture deficit in reducing the threshold values of both high-and low-temperature *** on the derived thresholds of climate extremes that impact vegetation productivity,Earth System Models project that southwestern TP and part of the northeastern TP will become the hotspots with a high exposure risk to climate extremes by *** study deciphers the high-impact extreme climates using two important thresholds across TP,which advances the understanding of the vegetation response to different climate extremes and provides a paradigm for assessing the impacts of climate extremes on regional ecosystems.

关键词： Tibetan Plateau Climate extremes Thresholds Vegetation productivity