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

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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Quantum Speed Limit under Brachistochrone Evolution

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Physical Review Applied 2023年第1期20卷 014031-014031页

作者： Fu-Quan Dou Min-Peng Han Chuan-Cun Shu College of Physics and Electronic Engineering Northwest Normal University Lanzhou 730070 China Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China

According to the Heisenberg uncertainty principle between time and energy fluctuation, a concept of the quantum speed limit (QSL) has been established to determine the minimum evolutionary time between quantum states. Considerable theoretical and experimental efforts are invested in obtaining the QSL time bounds in various scenarios. However, it remains a long-standing goal to derive a meaningful QSL bound for a general quantum problem. Here, we propose a geometrical approach to derive a QSL bound for closed and open quantum systems. By solving a quantum brachistochrone problem in the framework of the Riemannian metric, we show that the QSL between a given initial state and a final state is determined not only by the entire dynamics of the system but also by the individual dynamics of a critical parameter. We exemplify the utility of the bound in three representative scenarios, demonstrating a pronounced advantage in finding a tight and meaningful QSL bound of a general quantum evolution problem.

关键词： Cold atoms & matter waves Quantum control Quantum foundations Quantum state transfer Quantum transport Tunneling & traversal time Chaos & nonlinear dynamics Two-level models

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Revisiting the heterostructure and electric-field-modulation characteristics of the Ruddlesden-Popper perovskite Cs2Pb(SCN)2Br2 with low exciton-binding energy

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Physical Review Applied 2024年第6期22卷 064066-064066页

作者： Yan-Long Chen Jun Luo Biao Liu Jun-Liang Yang Hai-Lin Yu Meng-Qiu Cai Hunan Provincial Key Laboratory of High-Energy Scale Physics and Applications School of Physics and Electronics Hunan University Changsha 410082 People’s Republic of China Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics and Electronics Central South University Changsha 410083 Hunan People’s Republic of China School of Electronic and Information Engineering Changshu Institute of Technology Changshu 215500 People’s Republic of China

Two-dimensional Ruddlesden-Popper perovskites have garnered significant attention due to their excellent environmental stability, tunable photophysical properties, and other advantageous characteristics. Although two-dimensional perovskites have been extensively studied in the field of photoluminescence, their application in photovoltaics has been limited due to high exciton-binding energy. Recently, another Ruddlesden-Popper perovskite Cs2Pb(SCN)2Br2 has been synthesized. Compared to most two-dimensional perovskites, Cs2Pb(SCN)2Br2 boasts the advantages of low exciton-binding energy and a narrow optical band gap. To explore the potential of two-dimensional perovskites in photovoltaic applications, an all-inorganic two-dimensional heterojunction Cs2Pb(SCN)2Br2/MoS2 was investigated using first-principles calculations based on density-functional theory (DFT). Our calculation results demonstrate that the heterojunction exhibits significantly enhanced optical absorption properties and carrier mobility compared to Cs2Pb(SCN)2Br2 material. The heterojunction features a typical type-II band alignment, making it highly suitable for photovoltaic applications such as solar cells. We also applied a longitudinal electric field to the heterojunction in calculations, thereby regulating its band alignment. The calculation results reveal that the type-II band alignment of the heterojunction can be transformed into type-I and type-III alignments. These findings significantly expand the application potential of the heterojunction in electronic and optoelectronic devices.

关键词： Heterojunctions

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Vacuum deposited film growth,morphology and interfacial electronic structures of 2,7-dioctylbenzothieno[3,2-b]benzothiophene(C8-BTBT)

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Journal of Central South University 2022年第4期29卷 1041-1061页

作者： WEI Jun-hua NIU Dong-mei GAO Yong-li Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China Department of Physics and Astronomy University of RochesterRochesterNY 14627USA

Interfaces play critical roles in electronic devices and provide great diversity of film morphology and device *** retrospect the substrate mediated vacuum film growth of benchmark high mobility material 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene(C8-BTBT)and the interface electronic *** film growth of C8-BTBT molecules is diversified depending on the substrate-molecule and molecule-molecule *** atomic smooth substrates C8-BTBT film grows in layer-by-layer mode while on coarse substrate it grows in islands *** initial molecular layer at dielectric,semiconductor and conductive substrates displays slight different lattice *** initial molecule orientation depends on the substrate and will gradually change to standing up configuration as in bulk phase.C8-BTBT behaves as electron donor when contacting with dielectric and stable conductive *** usually induces a dipole layer pointing to C8-BTBT and an upward bend bending in C8-BTBT side toward the *** it is air stable,C8-BTBT is chemically reactive with some transition metals and *** orientation change from lying down to standing up in the film usually leads to decrease of ionization *** article provides insights to the interface physical and chemical processes and suggestions for optimal design and fabrication of C8-BTBT based devices.

关键词： interface film morphology packing configuration growth mode electronic structure chemical reaction interface dipole

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Visualizing vibrationally resolved attosecond time delay in resonance-enhanced multiphoton ionization of NO molecules

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Physical Review A 2023年第2期108卷 023114-023114页

作者： Xing Li Yong Liu Dongdong Zhang Lanhai He Sizuo Luo Chuan-Cun Shu Dajun Ding Institute of Atomic and Molecular Physics Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy Jilin University Changchun 130012 China Department of Physics Dalian University of Technology Dalian 116024 China Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China

We demonstrate a combined experimental and theoretical study to measure attosecond-resolved resonance-enhanced multiphoton ionization (REMPI) of NO molecules using the phase-locked strong 400-nm and weak 800-nm laser pulses. By performing the time-dependent wave-packet simulation, our results show that a vibrational-dependent REMPI occurs through two intermediate electronic states A2Σ+ and B2Π, from which a molecular wave packet at different internuclear distances results in an ionization time delay up to 630 as. We find that the nonadiabatic coupling between electronic states A2Σ+(ν=2) and B2Π(ν′=4) plays a crucial role in the angular-dependent phase variations of emitted electrons. This work extends the application of the REMPI technique to visualize the effect of vibrational motions of intermediate resonance states on the strong-field-induced ionization in attosecond timescales.

关键词： Multiphoton or tunneling ionization & excitation Stark effect Strong electromagnetic field effects Strong field excitation

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Enhanced interlayer neutral excitons and trions in MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure

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Nano Research 2022年第6期15卷 5640-5645页

作者： Biao Wu Haihong Zheng Shaofei Li Junnan Ding Jun He Zongwen Liu Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China State Key Laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia The University of Sydney Nano Institute The University of SydneyNSW 2006Australia Shenzhen Research Institute of Central South University Shenzhen 518057China

Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the design of optoelectronic ***,the bilayer heterostructure with type-II band alignment can only produce low quantum ***,we present the observation of interlayer neutral excitons and trions in the MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure(Tri-HS).In comparison to the 8 K bilayer heterostructure,the addition of a MoSe_(2)layer to the Tri-HS can significantly increase the quantum yield of *** is believed the two symmetrical type-II band alignments formed in the Tri-HS could effectively promote the IX radiation *** analyzing the photoluminescence(PL)spectrum of the IXs at cryogenic temperature and the power dependence,the existence of the interlayer trions was *** results provide a promising platform for the development of more efficient optoelectronic devices and the investigation of new physical properties of TMDs.

关键词： transitional metal dichalcogenide trilayer heterostructure enhanced interlayer exciton effect photoluminescence interlayer exciton

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Dynamic control of moirépotential in twisted WS_(2)-WSe_(2)heterostructures

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Nano Research 2022年第8期15卷 7688-7694页

作者： Shaofei Li Haihong Zheng Junnan Ding Biao Wu Jun He Zongwen Liu Yanping Liu School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China State Key Laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia The University of Sydney Nano Institute The University of SydneyNSW 2006Australia Shenzhen Research Institute of Central South University Shenzhen 518057China

Moirésuperlattices are formed by a lattice mismatch or twist angle in two-dimensional materials,which can generate periodical moirépotentials leading to strong changes in the band structure,resulting in new quantum ***,the experimental engineering of in-situ deformation of moiréheterostructures remains ***,we demonstrate a dynamic local deformation of the twisted heterostructures using a diamond anvil cell(DAC),enabling in-situ dynamic modulation of moirépotential in twisted WS_(2)–WSe_(2)heterostructures at room *** of the twisted heterostructure increases the moirépotential,causing a red shift of the moiréexciton resonance,and observed the red shift of the intralayer exciton resonance up to 16.3 meV(less than 1.1 GPa).The blue shift of the interlayer excitons of twisted WS_(2)–WSe_(2)heterostructures shows an evident transition of the pressure sensitive exciton,induced by the dominant effect of modifying the band structure on optical *** with the spectral changes of pressurized Raman,which further demonstrated that the DAC can efficiently regulate the interlayer *** results offer an effective strategy for in-situ dynamic modulation of moirépotential,providing a promising platform for the development of novel quantum devices.

关键词： moirésuperlattices twisted heterostructures moirépotential diamond anvil cell(DAC)

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ultrafast interfacial charge transfer and superior photoelectric conversion properties in one-dimensional Janus-MoSSe/WSe2 van der Waals heterostructures

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Physical Review B 2023年第4期108卷 045416-045416页

作者： Biao Cai Jianing Tan Long Zhang Degao Xu Jiansheng Dong Gang Ouyang Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province School of Physics and Electronics Hunan Normal University Changsha 410081 China Hunan Key Laboratory of Super Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices School of Physics and Electronics Central South University Changsha 410083 China Department of Physics Jishou University Jishou 416000 China

One-dimensional (1D) van der Waals (vdW) heterostructures have attracted great attention due to their excellent photoelectric properties which potentially serve as key components for next-generation optoelectronic devices. However, investigations on the photoelectric conversion properties in 1D vdW heterostructures are still in the rudimentary stage. Addressing the mechanism of the role of flexoelectricity in nanotubes and electronegativity difference of Janus materials on photoelectric properties remains challenging. In this paper, we investigate the flexoelectric effect and electronegativity difference on the photoelectric properties of 1D Janus-MoSSe/WSe2 vdW heterostructures and assess their potential for solar cells through the atomic-bond-relaxation approach combined with ab initio nonadiabatic molecular dynamics simulations. We find that a 1D MoSSe/WSe2 vdW heterostructure with AB1 stacking configuration exhibits ultrafast interfacial charge transfer and superior photoelectric conversion properties owing to the beneficial effects of flexoelectricity and electronegativity difference. Specifically, the photogenerated electron (hole) transfer in the 1D MoSSe/WSe2 system occurs quickly, within 55 (17) fs. Moreover, the optimal power conversion efficiency of 1D MoSSe/WSe2 vdW heterostructure-based solar cells can reach up to 6.25%, which is significantly higher than those of 1D MoS2/WSe2 (5.45%) and 2D MoSSe/WSe2 (1.94%). In this paper, we provide an effective strategy for the development of high-efficiency solar cells.

关键词： Flexoelectricity Optoelectronics Transition metal dichalcogenides

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Transverse Spin Selectivity in Helical Nanofibers Prepared without Any Chiral Molecule

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Physical Review Letters 2024年第10期133卷 108001页

作者： Chenchen Wang Zeng-Ren Liang Xiao-Feng Chen Ai-Min Guo Guanghao Ji Qing-Feng Sun Yong Yan CAS Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in Nanoscience Beijing 100049 China Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics International Center for Quantum Materials School of Physics Hefei National Laboratory Hefei 230088 China Department of Chemistry School of Chemistry and Biological Engineering

In the last decade, chirality-induced spin selectivity (CISS) has undergone intensive study. However, there remain several critical issues, such as the microscopic mechanism of CISS, especially transverse CISS where electrons are injected perpendicular to the helix axis of chiral molecules, quantitative agreement between experiments and theory, and at which level the molecular handedness is key to the CISS. Here, we address these issues by performing a combined experimental and theoretical study on conducting polyaniline helical nanofibers which are synthesized in the absence of any chiral species. Large spin polarization is measured in both left- and right-handed nanofibers for electrons injected perpendicular to their helix axis, and it will be reversed by switching the nanofiber handedness. We first develop a theoretical model to study this transverse CISS and quantitatively explain the experiment. Our results reveal that our theory provides a unifying scheme to interpret a number of CISS experiments, quantitative agreement between experiments and numerical calculations can be achieved by weak spin-orbit coupling, and the supramolecular handedness is sufficient for spin selectivity without any chiral species.

关键词： Chirality Spin polarization Spin-orbit coupling Transport phenomena Polymers Green's function methods Transport techniques

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