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Maximizing orientation of a three-state molecule in a cavity with analytically designed pulses

Physical Review A 2025年第3期111卷 033119-033119页

作者： Li-Bao Fan Hai-Ji Li Qi Chen Hang Zhou Heng Liu Chuan-Cun Shu 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 Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering School of Physics and Electronic Science Changsha University of Science and Technology Changsha 410114 China

We theoretically explore the precise control of a molecular polariton by strongly coupling the lowest three rotational states of a single molecule with a single-mode cavity. We examine two distinct cavity resonance configurations: a fundamental frequency cavity (ωc=2B with the rotational constant B) resonating with the lowest two rotational states, and a second harmonic cavity (ωc=4B) coupling with the first and second excited rotational states. We propose two control schemes based on the two polariton configurations and derive the corresponding pulse-area theorems to achieve a theoretical maximum orientation of 0.7746, identical to the molecule without the cavity. The control schemes are analyzed in carbonyl sulfide (OCS) molecules in their ground rotational state. Our numerical simulation results demonstrate the theoretical control schemes and analyze the sensitivity of the molecular polariton orientation degree to the control field bandwidth and phases. This work provides a valuable reference for achieving maximum field-free orientation of ultracold three-state molecules in a cavity using analytically designed pulses.

关键词： Molecular polarity

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Regulation of zero-dimensional metal halides by ions with ns2 lone-pair electronic structure derived from ns2np2 neutral atoms

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Physical Review Applied 2024年第6期22卷 064065-064065页

作者： Jun Luo Zhi-Ming Luo Biao Liu Jun-Liang Yang 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 Hunan 410083 China Greater Bay Area Institute for Innovation Hunan University Guangzhou 511300 China

Recently, low-dimensional metal halides have attracted considerable attention for their highly versatile tunability and outstanding broadband luminescence characteristics. Concurrently, there is an increasing number of studies focusing on the modulation of photoluminescence properties via doping, particularly with GSP2+ (Ge2+, Sn2+, and Pb2+) ions possessing ns2 lone-pair electrons (originating from neutral atoms with an ns2np2 electronic configuration), which are considered ideal dopants. However, numerous promising experimental outcomes resulting from doping depend significantly on empirical knowledge and fortuitous circumstances. Comprehensive theoretical research is crucial to effectively guide experimental approaches and minimize resource wastage. In this study, we employ GSP2+ ions doped into Cs2ZnBr4 as a model to explore the regulatory mechanisms and principles that govern the effects of various GSP2+ ions on zero-dimensional metal halides. Our findings indicate that GSP2+ ions doped into Cs2ZnBr4 form [MBr4]2− (M = Ge, Sn, and Pb) tetrahedra, which undergo deformation in the excited state, leading to self-trapping emissions in initially weak-luminescent Cs2ZnBr4. Additionally, there is a gradual decrease in the transition dipole moment and a continuous increase in emission energy from Cs2ZnBr4:Ge to Cs2ZnBr4:Sn to Cs2ZnBr4:Pb. Furthermore, the luminescence lifetime of Cs2ZnBr4:Pb is shorter than that of Cs2ZnBr4:Ge and Cs2ZnBr4:Sn, owing to the lower barrier for the singlet to triplet transition in Cs2ZnBr4:Pb. Our theoretical analysis will facilitate the development of more efficacious doping strategies in experimental settings.

关键词： Metal halides

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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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Regulation of Luminescence Properties of the Ultrathin Two-Dimensional Halide Perovskite Cs2PbIxCl4−x (x = 0,1,2,3,4) with Ruddlesden-Popper Structure

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Physical Review Applied 2023年第2期20卷 024047-024047页

作者： Jun Luo Biao Liu Jun-Liang Yang 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 China

The synthesized two-dimensional (2D) Ruddlesden-Popper (RP) all-inorganic mixed halogen perovskite, Cs2PbIxCl4−x (x = 2) has attracted extensive attention due to its excellent luminescence properties and environmental stability. However, the regulation of halogen ratio and halogen replacement sites on the luminescence properties of 2D RP inorganic mixed halogen perovskite remains unknown. In this paper, the luminescence properties containing band structures, effective mass, exciton-binding energies, photoluminescence emission energy, and the transition dipole moment of 2D RP perovskite Cs2PbIxCl4−x (x = 0,1,2,3,4) were studied via density-functional theory. To systematically represent different replacement sites, according to the halogens on the equatorial plane of the octahedron, we divide it into three types. [(1) the halogens on the equatorial plane are I atoms; (2) the halogens on the equatorial plane are Cl atoms; (3) the halogens on the equatorial plane are composed of I and Cl atoms]. The calculation results show that for structures with replacement sites of the same kind, the band gap, photoluminescence emission energy, and transition dipole moment decrease with the increase of the proportion of I atoms, while the opposite is true for exciton-binding energy and effective mass. In addition, among the three types of replacement sites, the quadratic eigenvalue problem-Mix (equatorial plane is composed of I and Cl) type replacement site is the most conducive to the luminescence performance of the material. Our theoretical study will provide guidance for the design and fabrication of highly luminescent 2D RP perovskite.

关键词： Electronic structure Optoelectronics 2-dimensional systems Perovskites Photovoltaic absorbers Semiconductor compounds Ab initio molecular dynamics Density functional calculations

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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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Single-metal atoms supported on HfBO MBenes for efficient overall water splitting

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RSC advances 2025年第24期15卷 19079-19087页

作者： Meiling Pan Xiuhua Cui Qun Jing Haiming Duan Fangping Ouyang Rong Wu Xinjiang Key Laboratory of Solid State Physics and Devices School of Physical Science and Technology Xinjiang University 777 Huarui Street Urumqi 830017 China xjcxh0991@*** dhm@***. School of Physics Hunan Key Laboratory for Super-Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices Central South University Changsha 410083 China oyfp@***.

Two-dimensional hexagonal MBenes (h-MBenes), derived from h-MAB phases, exhibit great potential for electrochemical applications due to their unique electronic and catalytic properties. Using first-principles calculations, we explored single-atom transition metals (TMs) supported on h-MBene HfBO (TM@HfBO) as bifunctional catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). TM@HfBO structures demonstrated excellent thermal stability and high electrical conductivity, making them suitable for electrocatalysis. For HER, Nb@HfBO showed outstanding activity with a near-ideal hydrogen adsorption free energy (Δ = -0.01 eV), surpassing even platinum. For OER, ferromagnetic TM@HfBO systems (TM = Fe, Co, Ni) exhibited high catalytic potential, with Ni@HfBO achieving the lowest overpotential ( = 0.48 V), outperforming IrO ( = 0.56 V). These results highlight TM@HfBO as a promising alternative to noble-metal-based catalysts. Our findings provide a foundation for designing cost-effective, high-performance electrocatalysts for overall water splitting and underscore the potential of HfBO-based materials in sustainable energy applications.

关键词： Iron

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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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Hybrid C8-BTBT/In GaAs nanowire heterojunction for artificial photosynaptic transistors

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Journal of Semiconductors 2022年第11期43卷 9-21页

作者： Yiling Nie Pengshan Xie Xu Chen Chenxing Jin Wanrong Liu Xiaofang Shi Yunchao Xu Yongyi Peng Johnny C.Ho Jia Sun Junliang Yang Hunan Key Laboratory for Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China Department of Materials Science and Engineering City University of Hong KongKowloon 999077Hong Kong SARChina State Key Laboratory of Terahertz and Millimeter Waves City University of Hong KongKowloon 999077Hong Kong SARChina Key Laboratory of Advanced Materials Processing&Mold(Zhengzhou University) Ministry of EducationZhengzhou 450002China

The emergence of light-tunable synaptic transistors provides opportunities to break through the von Neumann bottleneck and enable neuromorphic ***,a multifunctional synaptic transistor is constructed by using 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene(C8-BTBT)and indium gallium arsenide(InGaAs)nanowires(NWs)hybrid heterojunction thin film as the active *** illumination,the Type-I C8-BTBT/InGaAs NWs heterojunction would make the dissociated photogenerated excitons more difficult to *** persistent photoconductivity caused by charge trapping can then be used to mimic photosynaptic behaviors,including excitatory postsynaptic current,long/short-term memory and Pavlovian ***,a high classification accuracy of 89.72%can be achieved through the single-layer-perceptron hardware-based neural network built from C8-BTBT/InGaAs NWs synaptic ***,this work could provide new insights into the fabrication of high-performance optoelectronic synaptic devices.

关键词： photonic synaptic transistor C8-BTBT InGaAs heterojunction

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