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Band structures of strained kagome lattices

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Chinese physics B 2024年第2期33卷 456-463页

作者：徐露婷杨帆 center for Joint Quantum studies and department of physics School of ScienceTianjin UniversityTianjin 300354China Tianjin Key Laboratory of Low Dimensional Materials physics and Preparing Technology Department of PhysicsTianjin UniversityTianjin 300354China

Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy *** theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin *** is found that the Dirac points move with applied ***,the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction,forming a partially flat band with a region dispersionless along ky direction while dispersive along kx *** results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.

关键词： kagome lattice strain band structure engineering

Spontaneous Recovery in Directed Dynamical Networks

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Engineering 2024年第6期37卷 208-214页

作者： Xueming Liu Xian Yan H.Eugene Stanley School of Artificial Intelligence and Automation&The MOE Engineering Research center of Autonomous Intelligent Unmanned Systems&the Key Laboratory of Image Processing Huazhong University of Science and TechnologyWuhan 430074China center for polymer studies Department of PhysicsBoston UniversityBostonMA 02215USA

Complex networked systems,which range from biological systems in the natural world to infrastructure systems in the human-made world,can exhibit spontaneous recovery after a failure;for example,a brain may spontaneously return to normal after a seizure,and traffic flow can become smooth again after a *** studies on the spontaneous recovery of dynamical networks have been limited to undirected ***,most real-world networks are *** fill this gap,we build a model in which nodes may alternately fail and recover,and we develop a theoretical tool to analyze the recovery properties of directed dynamical *** find that the tool can accurately predict the final fraction of active nodes,and the prediction accuracy decreases as the fraction of bidirectional links in the network increases,which emphasizes the importance of directionality in network *** to different initial states,directed dynamical networks may show alternative stable states under the same control parameter,exhibiting hysteresis *** addition,for networks with finite sizes,the fraction of active nodes may jump back and forth between high and low states,mimicking repetitive failure-recovery *** findings could help clarify the system recovery mechanism and enable better design of networked systems with high resilience.

关键词： Network resilience Directed dynamical networks Spontaneous recovery

Collectively induced transparency and absorption in waveguide quantum electrodynamics with Bragg atom arrays

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Communications in Theoretical physics 2024年第8期76卷 19-28页

作者： Haolei Cheng Wei Nie center for Joint Quantum studies and department of physics School of ScienceTianjin UniversityTianjin 300350China Tianjin Key Laboratory of Low Dimensional Materials physics and Preparing Technology Tianjin UniversityTianjin 300350China

Collective quantum states, such as subradiant and superradiant states, are useful for controlling optical responses in many-body quantum systems. In this work, we study novel collective quantum phenomena in waveguide-coupled Bragg atom arrays with inhomogeneous *** atoms without free-space dissipation, collectively induced transparency is produced by destructive quantum interference between subradiant and superradiant states. In a large Bragg atom array, multi-frequency photon transparency can be obtained by considering atoms with different frequencies. Interestingly, we find collectively induced absorption(CIA) by studying the influence of free-space dissipation on photon transport. Tunable atomic frequencies nontrivially modify decay rates of subradiant states. When the decay rate of a subradiant state equals to the free-space dissipation, photon absorption can reach a limit at a certain frequency. In other words, photon absorption is enhanced with low free-space dissipation, distinct from previous photon detection schemes. We also show multi-frequency CIA by properly adjusting atomic frequencies. Our work presents a way to manipulate collective quantum states and exotic optical properties in waveguide quantum electrodynamics(QED) systems.

关键词： waveguide quantum electrodynamics collective quantum states photon absorption Bragg atom array

Highly efficient solution-processed organic photovoltaics enabled by improving packing behavior of organic semiconductors

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Science China Chemistry 2024年第3期67卷 890-897页

作者： Xinyue Cui Hongxiang Li Hao Lu Yuqiang Liu Guangliu Ran Rui Liu Huarui Zhang Xueqing Ma Dawei Li Yi Lin Jifa Yu Wenkai Zhang Lei Cai Yahui Liu Pei Cheng Andong Zhang Zaifei Ma Guanghao Lu Zhishan Bo College of Textiles and Clothing State Key Laboratory of Bio-fibers and Eco-textilesQingdao UniversityQingdao 266071China State Key Laboratory of polymer Materials Engineering College of Polymer Science and EngineeringSichuan UniversityChengdu 610065China department of physics and Applied Optics Beijing Area Major Laboratory Center for Advanced Quantum StudiesBeijing Normal UniversityBeijing 100875China Shandong Province Key Laboratory of Medical physics and Image Processing Technology School of Physics and ElectronicsShandong Normal UniversityJinan 250014China Beijing Key Laboratory of Energy Conversion and Storage Materials College of ChemistryBeijing Normal UniversityBeijing 100875China center for Advanced Low-Dimension Materials State Key Laboratory for Modification of Chemical Fibers and Polymer MaterialsCollege of Materials Science and EngineeringDonghua UniversityShanghai 201620China Frontier Institute of Science and Technology Xi'an Jiaotong UniversityXi'an 710054China

Solution processability is a unique property of organic semiconductors. The compact and regular π-π stacking between molecules is paramount in the performance of organic optoelectronic devices. However, it is still a challenge to improve their stacking quality without sacrificing the solution-processability from the aspect of materials design. Here, delicately engineered additives are presented to promote the formation of ordered aggregation of conjugated molecules by regulating their nucleation and growth dynamics. Intriguingly, the long-chain BTP-eC9-4F molecules can realize ordered aggregation comparable to short-chain ones without sacrificing processability. The domain size of BTP-eC9-4F aggregation is enlarged from 24.2 to 32.2 nm in blend *** exciton diffusion and charge transport become faster, contributing to the suppression of recombination losses. As a result, a power conversion efficiency of 19.2% is achieved in D18:BTP-eC9-4F based organic photovoltaics. Our findings demonstrate a facile strategy to improve the packing quality of solution-processed organic semiconductors for high-efficiency photovoltaics and beyond photovoltaics.

关键词： organic semiconductor organic photovoltaic charge transport solution processability

Kerr black hole shadows cast by extraordinary light rays with Weyl corrections

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Science China(physics,Mechanics & Astronomy) 2024年第5期67卷 18-26页

作者： Songbai Chen Jiliang Jing department of physics Institute of Interdisciplinary StudiesKey Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

We investigate the equation of motion for photons with Weyl corrections in a Kerr black hole spacetime in a small coupling *** results show that Weyl corrections yield phenomena of *** light rays propagating in the spacetime are separated into the ordinary rays and the extraordinary rays,and the propagation of the latter depends on the *** probe the effects of Weyl corrections on the Kerr black hole shadows casted by the extraordinary rays and find that such corrections result in a weak stretching or squeezing in the vertical direction for the black hole ***,we also study the change of the length of the Near-Horizon Extremal Kerr line(NHEK line)with Weyl *** features could help us to understand the electrodynamics with Weyl corrections from black hole shadows.

关键词： correction light stretching

Quasinormal modes and isospectrality of Bardeen(Anti-)de Sitter black holes

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Chinese physics C 2024年第3期48卷 191-202页

作者：赵莹刘文韬张超房熊俊荆继良 department of physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Educationand Synergetic Innovation Center for Quantum Effects and ApplicationsInstitute of Interdisciplinary StudiesHunan Normal UniversityChangsha 410081China department of physics Faculty of ScienceTokyo University of Science1-3KagurazakaShinjuku-kuTokyo 162-8601Japan

Black holes(BHs)exhibiting coordinate singularities but lacking essential singularities throughout the spacetime are referred to as regular black holes(RBHs).The initial formulation of RBHs was presented by Bardeen,who considered the Einstein equation coupled with a nonlinear electromagnetic *** this study,we investigate the gravitational perturbations,including the axial and polar sectors,of the Bardeen(Anti-)de Sitter black *** derive the master equations with source terms for both axial and polar perturbations and subsequently compute the quasinormal modes(QNMs)through numerical *** the Bardeen de Sitter black hole,we employ the 6thorder WKB *** numerical results reveal that the isospectrality is broken in this ***,the QNM frequencies are calculated using the HH method for the Bardeen Anti-de Sitter black hole.

关键词： Bardeen quasinormal modes master equation

Improved Reall-Santos method for AdS black holes in general 4-derivative gravities

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Science China(physics,Mechanics & Astronomy) 2024年第8期67卷 74-86页

作者： Peng-Ju Hu Liang Ma Hong Lü Yi Pang center for Joint Quantum studies and department of physics School of ScienceTianjin UniversityTianjin 300350China Joint School of National University of Singapore and Tianjin University International Campus of Tianjin UniversityFuzhou 350207China Peng Huanwu center for Fundamental Theory Hefei 230026China

For asymptotically flat black holes,Reall-Santos method is a convenient tool to compute leading higher derivative corrections to the thermodynamic quantities without actually solving the modified field ***,there are subtleties in its generalization to asymptotically AdS black holes with general higher derivative *** of all,it is necessary to know all the higher derivative holographic counterterms and the surface terms implementing the variational principle and subtracting the *** then needs to solve for the modified AdS radius and rescale the time coordinate in an appropriate way such that the induced metric on the conformal boundary of AdS black hole is not *** observe that Reall-Santos method can be directly applied to a particular 4-derivative gravity model,known as the Einstein-Weyl gravity,which does not modify the AdS radius and requires only the Gibbons-Hawking-York term and holographic counterterms for the 2-derivative *** thus suggest that to compute the thermodynamic quantities of AdS black holes in general 4-derivative theories of gravity,one simply needs to transform it to a Einstein-Weyl gravity with identical thermodynamic variables by appropriate field *** explicitly verify this proposal with spherically-symmetric and static charged black holes in Einstein-Maxwell theory extended with generic 4-derivative interactions.

关键词： black holes thermodynamics higher-derivative corrections effective theories higher dimensional black holes quantum gravity

Chiral bound states in a staggered array of coupled resonators

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Chinese physics B 2024年第2期33卷 124-130页

作者：金伍林李静卢竞龚志瑞周兰 Synergetic Innovation center for Quantum Effects and Applications Key Laboratory for Matter Microstructure and Function of Hunan ProvinceKey Laboratory of Low-Dimensional Quantum Structures and Quantum Control of the Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsInstitute of Interdisciplinary StudiesXiangjiang-Laboratory and Department of PhysicsHunan Normal UniversityChangsha 410081China College of physics and Optoelectronic Engineering Shenzhen UniversityShenzhen 518060China

We study the chiral bound states in a coupled-resonator array with staggered hopping strengths,which interacts with a two-level small atom through a single coupling point or two adjacent *** addition to the two typical bound states found above and below the energy bands,this system presents an extraordinary chiral bound state located within the energy *** use the chirality to quantify the breaking of the mirror *** find that the chirality value undergoes continuous changes by tuning the coupling *** preferred direction of the chirality is controlled not only by the competition between the intracell and the intercell hoppings in the coupled-resonator array,but also by the coherence between the two coupling *** the case with one coupling point,the chirality values varies monotonously with difference between the intracell hopping and the intercell *** in the case with two coupling points,due to the coherence between the two coupling points the perfect chiral states can be obtained.

关键词： bound states two-level small atom coupled-resonator array chirality

CuO–TiO_(2) based self-powered broad band photodetector

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Nano Materials Science 2024年第3期6卷 345-354页

作者： Chiranjib Ghosh Arka Dey Iman Biswas Rajeev Kumar Gupta Vikram Singh Yadav Ashish Yadav Neha Yadav Hongyu Zheng Mohamed Henini Aniruddha Mondal department of physics National Institute of Technology DurgapurWest BengalIndia department of physics University of Petroleum&Energy Studies DehradunUttarakhandIndia Babasaheb Bhimrao Ambedkar University Lucknow226031India center for Advanced Laser Manufacturing(CALM) Shandong University of TechnologyZibo255000PR China School of physics and Astronomy University of NottinghamNottinghamNG72RDUnited Kingdom

An efficient room-temperature self-powered,broadband(300 nm–1100 nm)photodetector based on a CuO–TiO_(2)/TiO_(2)/p-Si(100)heterostructure is *** CuO–TiO_(2)nanocomposites were grown in a two-zone horizontal tube furnace on a 40 nm TiO_(2)thin film deposited on a p-type Si(100)*** CuO–TiO_(2)/TiO_(2)/p-Si(100)devices exhibited excellent rectification characteristics under dark and individual photoillumination *** devices showed remarkable photo-response under broadband(300–1100 nm)light illumination at zero bias voltage,indicating the achievement of highly sensitive self-powered photodetectors at visible and near-infrared light *** maximum response of the devices is observed at 300 nm for an illumination power of 10 *** response and recovery times were calculated as 86 ms and 78 ms,***,under a small bias,the devices showed a prompt binary response by altering the current from positive to negative under illumination *** main reason behind this binary response is the low turn-on voltage and photovoltaic characteristics of the *** illumination conditions,the generation of photocurrent is due to the separation of photogenerated electron-hole pairs within the built-in electric field at the CuO–TiO_(2)/TiO_(2)*** characteristics make the CuO–TiO_(2)/TiO_(2)broadband photodetectors suitable for applications that require high response speeds and self-sufficient functionality.

关键词： Self-powered CuO–TiO_(2) nanocomposite Broadband photodetector Two-zone horizontal tube furnace Responsivity