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SSRN 2024年

作者： Bhat, Irfan Hussain Hu, Pei-Jia Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics Central South University Changsha410083 China

This study investigates the electron transport properties of two-terminal disordered graphene nanoribbons (GNRs), considering the presence of randomly distributed ``5-5-8" line defects (LDs). Although the presence of random LDs causes significant localization and suppression in conductance, attributed to Anderson localization, several robust conductance peaks, including a quantized peak, can be observed in the transmission spectra of disordered GNRs regardless of sizes and LD concentrations. Furthermore, the study demonstrates that the width, particularly the edge configuration of disordered GNRs, significantly affects these peaks. In the case of symmetric edge configurations, the number of peaks remains constant, but their positions shift as the width increases. In contrast, for asymmetric edge configurations, the number and positions of the peaks change with width. Notably, a quantized conductance peak regardless of various configurations is observed. The study offer valuable insights for the design GNR devices based on LDs and edge symmetry. © 2024, The Authors. All rights reserved.

关键词： Graphene

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

arXiv

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arXiv 2024年

作者： Fan, Li-Bao Li, Hai-Ji Chen, Qi Zhou, Hang Liu, Heng 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

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 in the absence of 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. Copyright © 2024, The Authors. All rights reserved.

关键词： Molecular polarity

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Interface engineering of FAPbI_(3) for passivating defects and improving stability with lead chalcogenides

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Journal of Central South University 2024年第12期31卷 4625-4637页

作者： LI Yun-hao FENG Xiang-xiang LONG Meng-qiu CAI Meng-qiu YANG Jun-liang LIU Biao Hunan Key Laboratory of Nanophotonics and Devices School of PhysicsCentral South UniversityChangsha 410083China Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of PhysicsCentral South UniversityChangsha 410083China School of Physics and Electronics Science Hunan UniversityChangsha 410082China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

Interface engineering is widely employed to enhance the performance of formamidinium lead triiodide(FAPbI_(3))perovskite solar *** this study,six different FAPbI_(3)/PbX(X=S,Se and Te)heterostructures are constructed,including the PbI interface and I interface *** addition,the lead vacancies(V-Pb)and iodine vacancies(V-I)are designed at the perovskite *** results show that the PbI interface is more stable than I interface in the *** PbX covering layer on the surface of the FAPbI_(3) perovskite stabilizes the perovskite octahedral structure by interface interactions and charge reconstruction that are beneficial to passivate perovskite interface defects and inhibit the phase *** shows that the PbTe covering layer exhibits the best passivation effect for lead vacancy defects,while PbS covering layer shows the best passivation effect for iodine vacancy ***,appropriate structural stress can strengthen the thermal stability of defective *** work reveals the FAPbI_(3)/PbX interface engineering,and offers new insights into effectively passivating defects and improving the stability of FAPbI_(3).

关键词： interface engineering FAPbI_(3) PbX PSCs stability

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Strong anharmonicity-assisted low lattice thermal conductivities and high thermoelectric performance in double-anion Mo_(2)AB_(2)(A=S,Se,Te;B=Cl,Br,I)semiconductors

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Chinese Physics B 2023年第10期32卷 600-608页

作者：廖海俊黄乐谢兴董华锋吴福根孙志鹏李京波 School of Materials and Energy Guangdong University of TechnologyGuangzhou 510006China Guangdong Provincial Key Laboratory of Information Photonics Technology Guangdong University of TechnologyGuangzhou 510006China School of Physics and Optoelectronic Engineering Guangdong University of TechnologyGuangzhou 510006China School of Physics and Electronics Hunan Key Laboratory for Super-microstructure and Ultrafast ProcessCentral South UniversityChangsha 410083China College of Optical Science and Engineering Zhejiang UniversityHangzhou 310027China

The thermoelectric properties of layered Mo_(2)AB_(2)(A=S,Se,Te;B=Cl,Br,I)materials are systematically investigated by first-principles *** transverse acoustic modes and direct Mo d–Mo d couplings give rise to strong anharmonicities and low lattice thermal *** double anions with distinctly different electronegativities of Mo_(2)AB_(2)monolayers can reduce the correlation between electron transport and phonon scattering,and further benefit much to their good thermoelectric *** properties of these Mo_(2)AB_(2)monolayers exhibit obvious anisotropies due to the direction-dependent chemical bondings and transport ***,their thermoelectric properties strongly depend on carrier type(n-type or p-type),carrier concentration and *** is found that n-type Mo_(2)AB_(2)monolayers can be excellent thermoelectric materials with high electric conductivity,σ,and figures of merit,*** the types of A and B anions of Mo_(2)AB_(2)is an effective strategy to optimize their thermoelectric *** results provide rigorous understanding on thermoelectric properties of double-anions compounds and important guidance for achieving high thermoelectric performance in multi-anion compounds.

关键词： thermoelectricity anharmonicity lattice thermal conductivity anisotropy first-principles calculations

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Defects in ultraflat germanene on Cu(111)

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Physical Review B 2024年第12期110卷 125430页

作者： Qiwei Tian Xiao Guo Sahar Izadi Vishkayi Meysam Bagheri Tagani Li Zhang Yuan Tian Long-Jing Yin Han Huang Lijie Zhang Zhihui Qin Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices School of Physics and Electronics Hunan Key Laboratory of Super-microstructure and Ultrafast Process School of Physics School of Physics Department of Physics

Germanene is one of the most promising two-dimensional materials beyond graphene. The electronic properties of germanene are outstanding. However, structural defects, which may appear during growth or processing, deteriorating the performance of germanene-based devices, are elusive. Here, we combine scanning tunneling microscopy/spectroscopy, Raman spectroscopy, and density functional theory calculations to investigate the defects in epitaxial ultraflat germanene on Cu(111). Three types of defects are found and their electronic properties are explored. Single germanium atom vacancy leads to three well-defined states in local density of states, whereas the mirror twin boundary induced four electronic states confirmed by theoretical calculations. Furthermore, strain induced wrinkles with enhanced electronic states occurred in ultraflat germanene. In addition, we synthesized bi- and trilayer germanene with significant different electronic properties, where a tiny band gap is opened due to the symmetry breaking.

关键词： Germanene Density functional theory Scanning tunneling microscopy Scanning tunneling spectroscopy

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Giant valley polarization and perpendicular magnetocrystalline anisotropy energy in monolayer MX2 (M=Ru,Os;X=Cl,Br)

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Physical Review B 2024年第2期109卷 024406-024406页

作者： Weifeng Xie Long Zhang Yunliang Yue Min Li Hui Wang School of Physics Hunan Key Laboratory of Super Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China College of Information Engineering Yangzhou University Yangzhou 225127 China

Large valley polarization and perpendicular magnetocrystalline anisotropy energy (PMAE) in room-temperature ferrovalley materials has been pursued for a long time because PMAE not only stabilizes long-range ferromagnetic (FM) order but also ensures spontaneous valley polarization. Herein, valley polarization and MAE of monolayer MX2 (M=Ru,Os; X=Cl,Br) are investigated based on first-principles calculations, Wannier functions, and Monte Carlo simulations. It is found that OsBr2 has a giant valley polarization of 327.158 meV and PMAE of 10.354 meV, ascribing to the strong spin-orbital coupling. The physical mechanism of valley polarization and PMAE are analyzed both qualitatively and quantitatively on the basis of perturbation theory, which shows that the valley polarization induces the distribution of MAE at K and K′ valley points with opposite signs, and the couplings between dz2 and dyz, dxz and dxy, and dx2−y2 and dyz in opposite spin channels through orbital angular momentum operator L̂x have a dominant contribution to the total MAE. Moreover, doping of a few holes and biaxial compressive strain both remarkably improve the PMAE of OsBr2. Meanwhile, the compressive strain can enhance FM exchange coupling of OsBr2, increasing the Curie temperature Tc far beyond the room temperature. Additionally, doping of a few electrons can significantly increase the PMAE of room-temperature ferrovalley OsCl2 to reach ∼40 meV. In this paper, we elucidate the physical mechanism of the valley polarization and MAE and indicate that monolayer OsCl2 and OsBr2 are promising for application in valleytronic and magnetic storage devices at room-temperature condition.

关键词： Magnetic anisotropy Spin-orbit coupling Valleytronics 2-dimensional systems Density functional calculations Monte Carlo methods

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Organic solar cells with D18 or derivatives offer efficiency over 19%

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Journal of Semiconductors 2024年第5期45卷 1-4页

作者： Erming Feng Chujun Zhang Jianhui Chang Hengyue Li Liming Ding Junliang Yang Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of PhysicsCentral South UniversityChangsha 410083China Center for Excellence in Nanoscience Key Laboratory of Nanosystem and Hierarchical Fabrication(CAS)National Center for Nanoscience and TechnologyBeijing 100190China

In recent years,organic solar cells(OSCs)have garnered significant attention due to their distinctive attributes,such as flexibility,lightweight,and solution processing,which position them as alternatives for next-generation solar technologies[1−5].Thanks to breakthroughs in materials development,the power conversion efficiency(PCE)for single-junction OSCs has already surpassed 19%[6−13].The development of photoactive materials is pivotal in enhancing the PCEs,and several reviews have provided insights into materials design[14−18].Herein,we highlight single-junction OSCs based on D18 and its derivatives[19,20].

关键词： breakthrough insight derivatives

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Evidence for interlayer coupling and moiréexcitons in twisted WS_(2)/WS_(2)homostructure superlattices

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Nano Research 2023年第2期16卷 3429-3434页

作者： Haihong Zheng Biao Wu Shaofei Li Jun He Keqiu Chen 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 Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China 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 518000China

The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)*** graphene and transition metal dichalcogenides(TMDs)moirésystems,twist angle has been shown to be a key parameter for regulating the moiré***,the effect of the modulation of the twist angle on moirépotential and interlayer coupling has not been the subject of experimental ***,we report the observation of the modulation of moirépotential and intralayer excitons in the WS_(2)/WS_(2)*** accurately adjusting the torsion angle of the homobilayers,the depth of the moirépotential can be *** confinement effect of the moirépotential on the intralayer excitons was further demonstrated by the changing of temperature and valley ***,we show that a detection of atomic reconstructions by the low-frequency Raman mapping to map out inhomogeneities in moirélattices on a large scale,which endows the uniformity of interlayer *** results provide insights for an in-depth understanding of the behaviors of moiréexcitons in the twisted van der Waals homostructure,and promote the study of electrical engineering and topological photonics.

关键词： moirésuperlattices moiréexcitons interlayer coupling moirépotential

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Trimetallic oxyhydroxides as active sites for large-current-density alkaline oxygen evolution and overall water splitting

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Journal of Materials Science & Technology 2022年第15期110卷 128-135页

作者： Lei Chen Yunpeng Wang Xin Zhao Yuchao Wang Qian Li Qichen Wang Yougen Tang Yongpeng Lei State Key Laboratory of Powder Metallurgy Hunan Key Laboratory of Two-Dimensional MaterialsCentral South UniversityChangsha 410083China Hunan Provincial Key Laboratory of Chemical Power Sources College of Chemistry and Chemical EngineeringCentral South UniversityChangsha 410083China School of Physics and Electronics Hunan Key Laboratory for Super-micro structure and Ultrafast ProcessCentral South UniversityChangsha 410083China

Earth-abundant electrocatalysts for large-current-density water splitting under alkaline condition are *** evolution reaction,which is a bottleneck of the overall water splitting,faces the problems of complicated reconstruction and deficiency in rational design of active ***,we report a series of transition metal chalcogenides for alkaline *** them,FeCoNi(S)displayed a low overpotential of 293 m V to deliver a current density of 500 m A cm^(-2),which is in the top level of non-precious metal based OER electrocatalysts.A combination of(ex)in situ characterizations and DFT calculation shows that Ni(Fe,Co)trimetallic oxyhydroxides were the active sites for highly-efficient ***,for FeCoNi(S),when used as a bifunctional catalyst for water splitting,it only required a cell voltage of 1.84 V to deliver~500 m A cm^(-2) with extraordinary long-term stability over 2000 *** work provides the comprehension of high-efficiency,robust catalysts for OER and overall water splitting at large current densities in alkaline media.

关键词： Oxygen evolution Active sites Surface reconstruction Large current density Overall water splitting

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一步水热法合成多孔氧缺陷镍铝双金属氢氧化物及其高电容存储

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Journal of Central South University 2023年第12期30卷 4138-4148页

作者：刘少波赵勇峰李恒月阳军亮 Hunan Key Laboratory for Super Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering School of Physics and Electronic ScienceChangsha University of Science and TechnologyChangsha 410114China

层状双金属氢氧化物(LDH)由于具有层状结构、丰富的氧化还原活性中心和金属离子间的协同作用被认为是超级电容器的理想电极之一。然而,低的比电容和较差的循环稳定性极大地限制了它们的规模化应用。本文采用简单的一步水热法在泡沫镍上... 详细信息

层状双金属氢氧化物(LDH)由于具有层状结构、丰富的氧化还原活性中心和金属离子间的协同作用被认为是超级电容器的理想电极之一。然而,低的比电容和较差的循环稳定性极大地限制了它们的规模化应用。本文采用简单的一步水热法在泡沫镍上制备层状镍铝双金属氢氧化物(NiAl-LDH),并通过不同的反应物浓度控制其电荷存储能力。研究发现反应物浓度对NiAl-LDH的形貌、结晶度和负载密度有明显调节作用。优化后的NiAl-LDH(Ni1Al1-LDH)具有丰富氧缺陷的多孔纳米片结构,该结构紧密包覆在高导电性泡沫镍表面,促进了离子和电子的转移,有效提高了Ni离子的氧化还原活性,从而提高了能量储存能力。作为超级电容器电极,Ni1Al1-LDH在电流密度为1 A/g时的比电容为1958.1 F/g。在100 mV/s的扫速下,经过1000次持续充放电循环,电容保持率高达108.7%。

关键词：超级电容器电容层状镍铝双金属氢氧化物多孔纳米片氧缺陷

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