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Confined subdiffusion in three dimensions

Chinese Physics B 2014年第11期23卷 145-151页

作者：覃善林何勇 Hunan Key Laboratory for Super-microstructure and Ultrafast Process Institute of Super Microstructure and Ultrafast Process in Advanced MaterialsSchool of Physics and Electronics Central South University

Three-dimensional （3D） Fick＇s diffusion equation and fractional diffusion equation are solved for different reflecting boundaries. We use the continuous time random walk model （CTRW） to investigate the time-averaged mean square dis- placement （MSD） of a 3D single particle trajectory. Theoretical results show that the ensemble average of the time-averaged MSD can be expressed analytically by a Mittag-Leffler function. Our new expression is in agreement with previous formu- las in two limiting cases：（^-δ2） ~ △1 in short lag time and （^-δ2} ~ △1 -α in long lag time. We also simulate the experimental data of mRNA diffusion in living E. coli using a 3D CTRW model under confined and crowded conditions. The simulation results are well consistent with experimental results. The calculations of power spectral density （PSD） further indicate the subdiffsive behavior of an individual trajectory.

关键词： confined subdiffusion three dimensions time-averaged mean squared displacement

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Tuning the magnetic state and topological transition of monolayer Kagome Co3Pb3SSe with large magnetic anisotropy

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Journal of Materials Chemistry C 2025年第21期13卷 10924-10930页

作者： Li, Yating Zhou, Wenzhe Li, Chuyu He, Xianjuan Ouyang, Fangping School of Physics Hunan Key Laboratory for Super-Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices Central South University Changsha410083 China School of Physics and Technology State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources Xinjiang University Urumqi830046 China State Key Laboratory of Powder Metallurgy Powder Metallurgy Research Institute Central South University Changsha410083 China

Ferromagnetic topological insulators (TIs) have recently garnered tremendous attention as a platform for investigating novel physical phenomena and innovative design of low-power-consumption spintronic devices. Co3X3Y2 monolayers are a promising topological system with a large quantum anomalous Hall effect (QAHE), but they suffer from low magnetic anisotropy. To address this limitation, we construct a Janus Kagome Co3Pb3SSe monolayer by introducing heavy elements to enhance spin-orbit coupling (SOC) and break mirror symmetry. Janus Co3Pb3SSe is a Weyl semimetal with a high Chern number (|C| = 3) and a substantial magnetic anisotropy of 2.613 meV per unit. It also exhibits a large band gap of 79.8 meV, which is robust against external strain, and a Curie temperature (TC) of 167 K. Notably, strain can induce multistate transitions in the material. Under a strain of −1%, attributed to the combined effects of super-exchange and direct exchange, there is a magnetic ground state transition from ferromagnetic (FM) to antiferromagnetic (AFM). At a strain of −2%, a phase transition from a topological insulator (TI) to a metallic state is observed. Under a 5% tensile strain, TC significantly increases to 348 K, thus enabling the material to be applied at room temperature. Our findings enrich researches on ferromagnetic TIs of Janus Kagome systems. © 2025 The Royal Society of Chemistry.

关键词： Ferromagnetism

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Low-temperature-cured highly conductive composite of Ag nanowires & polyvinyl alcohol

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Chinese Physics B 2017年第7期26卷 426-432页

作者：何松张祥杨兵初徐晓梅陈辉周聪华 Hunan Key Laboratory of Super-microstructure and Ultrafast Process School of Physics and ElectronicsCentral South University

Flexible conductive films were fabricated from a low-temperature-cured, highly conductive composite of silver nanowires （as conducting filler） and polyvinyl alcohol （PVA, as binder）. Sheet resistance of 0.12 Ω/sq, conductivity of 2.63 ×10^4 S/cm, and contact resistance of 1.0Ω/cm^2 were measured in the films, along with excellent resistance to scratch- ing and good flexibility, making them suitable electrical contact materials for flexible optoelectronic devices. Effects of curing temperature, curing duration, film thickness, and nanowire length on the film＇s electrical properties were studied. Due to the abundance of hydroxyl groups on its molecular chains, the addition of PVA improves the film＇s flexibility and resistance to scratching. Increased nanowire density and nanowire length benefit film conductance. Monte Carlo simulation was used to further explore the impact of these two parameters on the conductivity. It was observed that longer nanowires produce a higher length-ratio of conducting routes in the networks, giving better film conductivity.

关键词： conductive composite polyvinyl alcohol silver nanowires Monte Carlo simulation

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Cascaded plasmonic nanorod antenna for large broadband local electric field enhancement

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Chinese Physics B 2019年第10期28卷 535-540页

作者： Dou Zhang Zhong-Jian Yang Jun He Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South University

We propose a cascaded plasmonic nanorod antenna for large broadband electric near-field enhancement. The structure has one big gold nanorod on each side of a small two-wire antenna which consists of two small gold nanorods. For each small nanorod, the enhanced and broadened optical response can be obtained due to the efficient energy transfer from its adjacent big nanorod through strong plasmonic near-field coupling. Thus, the electric field intensity of the cascaded antenna is significantly larger and broader than that of the individual small two-wire antenna. The resonant position, field intensity enhancement, and spectral width of the cascaded antenna are highly tunable by varying the geometry of the system. The quantum efficiency of the cascaded antenna is also greatly enhanced compared with that of the small antenna. Our results are important for the applications in field-enhanced spectroscopy.

关键词： surface plasmon optical antenna electric field enhancement broadband cascaded

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Plasmon-assisted channel-tunable bistable states in a monolayer MoS2 nanoresonator coupled to a metallic nanoshell

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Optics Express 2025年第11期33卷 23568-23578页

作者： Jian-Bo Li Hong-Mei Gong Yu-Xiang Peng Si Xiao Jin-Bo Hu Lin-Wen Long Department of Physics Hunan Province Key Laboratory of Materials Surface & Interface Science and Technology Central South University of Forestry and Technology Changsha 410004 China jbli_opt@*** jbli_opt@*** School of Optical and Electronic Information & Jiangsu/Suzhou Key Laboratory of Biophotonics & International Joint Metacenter for Advanced Photonics and Electronics Suzhou City University Suzhou 215104 China hmgong@*** School of Physics Hunan Key Laboratory of Super microstructure and Ultrafast Process Central South University Changsha 410083 China sixiao@*** College of Materials and Energy Central South University of Forestry and Technology Changsha 410004 China

We study how to obtain the channel-tunable bistable states in a coupled system consisting of a monolayer MoS 2 nanomechanical resonator (NR) and a metallic nanoshell (MNS) beyond the dipole approximation. The MNS is constructed by a metallic core and a dielectric shell. The calculated results show that the linear absorption spectrum exhibits some new features, such as three-phonon resonance, Rayleigh resonance, and ac-Stark resonance. In a strong exciton-plasmon coupling regime, the absorption peak and amplification peak in the absorption spectrum can be greatly enhanced by adjusting the exciton-phonon coupling strength. Especially, we plot the bistability phase diagrams in the system’s parameter space and highlight the strong dependency of the lower (upper) bistable threshold on the pumping intensity, the MNS-NR distance, and the dielectric shell thickness. The ratio of linear absorption in the upper and lower stable states can reach 42. For a given MNS with a fixed shell thickness, it is easy to achieve single-channel or dual-channel bistable states by only adjusting the exciton-phonon coupling strength via modulation of the length of the MoS 2 nanosheet along the NR axis. The findings obtained here are very useful for extensive applications such as optical memory cells and channel-tunable bistable switches.

关键词： Absorption spectroscopy Light propagation Metal nanoparticles Nonlinear absorption Optical properties Slow light

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Polymer-Decorated 2D MoS2 Synaptic Transistors for Biological Bipolar Metaplasticities Emulation

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Chinese Physics Letters 2020年第8期37卷 177-188页

作者： Yuhang Zhao Biao Liu Junliang Yang Jun He Jie Jiang Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China

Biological bipolar metaplasticities were successfully mimicked in two-dimensional(2D)MoS2 transistors via the implementation of two different MoS2 surface decorations,poly(vinyl alcohol)(PVA)and chitosan ***,the depressing metaplasticity was successfully mimicked when the PVA bio-polymer was used as the surface decoration layer,whereas the metaplasticity of long-term potentiation was realized when the chitosan bio-polymer was taken as the surface decoration ***,the electronic band structures of the 2D MoS2 devices with different surface decorations were further investigated using first-principles calculations for understanding the underlying mechanisms of such bipolar *** results will deepen our understanding of metaplasticity,and have great potential in neuromorphic computing applications.

关键词： MoS2 poly(vinyl plasticity

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Highly stretchable polymer/silver nanowires composite sensor for human health monitoring

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Nano Research 2020年第4期13卷 919-926页

作者： Yanjing Zhang Pei He Meng Luo Xiaowen Xu Guozhang Dai Junliang Yang Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China

Flexible strain sensors exhibit outstanding advantages in terms of sensitivity and stability by detecting changes in physical *** can be easily attached to human skin and clothed to achieve monitoring of human motion and ***,general sensing material shows low stretchability and cannot respond to signals under large *** this work,a highly stretchable polymer composite was developed by adding small amount(0.17 wt.%)of silver nanowires(AgNWs)in stretchable conductive polymer *** conductivity of polymer/AgNWs composite is 1.3 S/m with the stretchability up to 500%.The stretchable strain sensor based on the polymer/AgNWs composite can respond to strain signals in real time,even for 1%strain response,and shows excellent stability over 1,000 loading/unloading ***,the strain sensor can be attached to human skin and clothed to monitor joints,throat and pulse of the human *** human body electrocardiogram(ECG)signal was detected successfully with the polymer/AgNWs electrode,which is comparable to the signal obtained by the commercial ***,the sensors enable monitoring of human movement and *** advantages make it a potential application in wearable devices and electronic skin.

关键词： stretchable sensor silver nanowires health monitoring electrocardiogram

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Dependence of Nonlinear Optical Response of Anatase TiO2 on Shape and Excitation Intensity

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Chinese Physics Letters 2017年第7期34卷 266-270页

作者：郭路华王迎威蒋永强肖思何军 Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of Physics and Electronics Central South University Changsha 410083

Nonlinear optical （NLO） properties of anatase TiO2 with nanostructures of nanopaxticle （NP）, nanowire （NW） and annealed nanowire （NWA） are studied by open-aperture and closed-aperture Z-scan techniques with a fem- tosecond pulsed laser at wavelengths of 532 nm and 780 nm simultaneously. At 532 nm, when increasing excitation intensity, NLO absorption of TiO2 NPs transforms from saturable absorption to reverse-saturable absorption. However, NWs and NWAs exhibit the opposite change. At 780nm, all samples show reverse-saturable absorption, but have different sensitivities to excitation intensity. Due to the larger surface-to-volume ratio of NPs and less defects of NWAs by annealing, nonlinear optical absorption coet^icients follow the order NPs≥ NWs≥ NWAs. The results also show that these shape and annealing effects axe dominant at low excitation intensity, but do not exhibit at the high excitation intensity. The NLO refractive index of NPs shows a positive linear relationship with the excitation intensity, whereas NW and NWAs exhibit a negative linear relationship. The results could provide some foundational guidance to applications of anatase TiO2 in optoelectronic devices or other aspects.

关键词： NP Dependence of Nonlinear Optical Response of Anatase TiO2 on Shape and Excitation Intensity NLO TiO

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Fano resonances in heterogeneous dimers of silicon and gold nanospheres

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Frontiers of physics 2018年第3期13卷 121-127页

作者： Qian Zhao Zhong-Jian Yang Jun He Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of Physics and Electronics Central South University Changsha 410083 China

We theoretically investigate the optical properties of dimers consisting of a gold nanosphere and a silicon nanosphere. The absorption spectrum of the gold sphere in the dimer can be significantly altered and exhibits a pronounced Fano profile. Analytical Mie theory and numerical simulations show that the Fano profile is induced by constructive and destructive interference between the incident electric field and the electric field of the magnetic dipole mode of the silicon sphere in a narrow wavelength range. The effects of the silicon sphere size, distance between the two spheres, and excitation configuration on the optical responses of the dimers are studied. Our study reveals the coherent feature of the electric fields of magnetic dipole modes in dielectric nanostructures and the strong interactions of the coherent fields with other nanophotonic structures.

关键词： silicon nanosphere gold nanosphere magnetic dipole resonance Fano resonance Mie theory

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Precise Quantum Control of Molecular Rotation Toward a Desired Orientation

arXiv

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arXiv 2025年

作者： Hong, Qian-Qian Dong, Daoyi Henriksen, Niels E. Nori, Franco He, Jun Shu, Chuan-Cun Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha410083 China Australian Artificial Intelligence Institute Faculty of Engineering and Information Technology University of Technology SydneyNSW2007 Australia Department of Chemistry Technical University of Denmark Building 207 Kongens LyngbyDK-2800 Denmark Quantum Computing Center Theoretical Quantum Physics Laboratory RIKEN Saitama351-0198 Japan Physics Department University of Michigan Ann ArborMI48109 United States

The lack of a direct map between control fields and desired control objectives poses a significant challenge in applying quantum control theory to quantum technologies. Here, we propose an analytical framework to precisely control a limited set of quantum states and construct desired coherent superpositions using a well-designed laser pulse sequence with optimal amplitudes, phases, and delays. This theoretical framework that corresponds to a multi-level pulse-area theorem establishes a straightforward mapping between the control parameters of the pulse sequence and the amplitudes and phases of rotational states within a specific subspace. As an example, we utilize this approach to generate 15 distinct and desired rotational superpositions of ultracold polar molecules, leading to 15 desired field-free molecular orientations. By optimizing the superposition of the lowest 16 rotational states, we demonstrate that this approach can achieve a maximum orientation value of |〈cos θ〉|max above 0.99, which is very close to the global optimal value of 1 that could be achieved in an infinite-dimensional state space. This work marks a significant advancement in achieving precise control over multi-level subsystems within molecules. It holds potential applications in molecular alignment and orientation, as well as in various interdisciplinary fields related to the precise quantum control of ultracold polar molecules, opening up considerable opportunities in molecular-based quantum techniques. © 2025, CC BY.

关键词： Molecular orientation

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