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High thermoelectric performance induced by strong anharmonicity in ternary Li-based chalcogenides

Physical Review B 2024年第15期110卷 155202页

作者： Linyuan Cheng Min Li Long Zhang 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

Thermoelectric materials enable heat-to-electricity conversion, while its efficiency has so far been restricted by the dimensionless figure of merit (ZT). In this study, we employ first-principles calculations combined with Boltzmann transport equation along with the thermal transport unified theory to investigate the electrical and thermal transport properties of a family of Li-based chalcogenides (Li3BX4, B=V, Nb, Ta and X=S, Se, Te). It is found that Li3BTe4 exhibit ultralow lattice thermal conductivity (κL) at room temperature, as lows as ∼0.1 W/mK. This is mainly attributed to the relatively weak interaction between the B and Te atom as confirmed by the small number of bonding states below the Fermi level, which introduces strong anharmonicity and significantly enhances the phonon scattering rate. Moreover, the observed power factors of Li3BTe4 are more than 10 µWcm−1K−2 at 300 K, giving rise to giant ZT at intermediate and high temperatures in both p-type and n-type, for instance, ZT reaches 2.25 ∼ 2.46 in Li3NbTe4 even after considering both particlelike propagation and wavelike phonon tunneling transport mechanism. In addition, we find that ZT of Li3BX4 can further be enhanced through moderate strain engineering and these Li-based chalcogenides exhibit high ductility which is favorable for the post machining process. The present work unravels the importance of strong anharmonicity induced by weak-bonded heavy element on the thermoelectric performance in Li3BX4 family which provides important insights for the rational design of flexible thermoelectric devices.

关键词： Anharmonic lattice dynamics Electron-phonon coupling Electronic structure Phonons Scattering theory Seebeck effect Thermal conductivity Thermoelectric effects Thermoelectrics 3-dimensional systems Chalcogenides Ab initio molecular dynamics Boltzmann theory Density functional calculations Density functional theory First-principles calculations

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Room-temperature ferromagnetism and half-metallicity in monolayer orthorhombic CrS_(2)

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Frontiers of physics 2024年第4期19卷 137-146页

作者：雷博程李奥林周文哲王云鹏熊威陈羽欧阳方平 School of Physics Science and Technology and Xinjiang Key Laboratory of Solid-State Physics and DevicesXinjiang UniversityUrumqi 830046China School of Physics and Hunan Key Laboratory for Super-Microstructure and Ultrafast Processand Hunan Key Laboratory of Nanophotonics and DevicesCentral South UniversityChangsha 410083China School of Physics Science and Technology and Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matter PhysicsYili Normal UniversityYining 835000China Powder Metallurgy Research Institute and State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

Two-dimensional materials with high-temperature ferromagnetism and half-metallicity have the latest applications in spintronic *** on first-principles calculations,we have investigated a novel two-dimensional CrS_(2) phase with an orthorhombic *** results suggest that it is stable in dynamics,thermodynamics,and *** ground state of monolayer orthorhombic CrS_(2) is both ferromagnetic and half-metallic,with a high Curie temperature of 895 K and a large spin-flipping gap on values of 0.804 *** room-temperature ferromagnetism and halfmetallicity can maintain stability against a strong biaxial strain ranging from–5%to 5%.Meanwhile,increasing strain can significantly maintain the out-of-plane magnetic anisotropy.A density of states analysis,together with the orbital-resolved magnetic anisotropy energy,has revealed that the strain-enhanced MAE is highly related to the 3d-orbital splitting of Cr *** results suggest the monolayer orthorhombic CrS_(2) is an ideal candidate for future spintronics.

关键词： orthorhombic CrS_(2) Curie temperature magnetic anisotropy energy biaxial strain first-principles calculations

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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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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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Protection of entanglement between two V-atoms in a multi-cavity coupling system

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Chinese Physics B 2022年第1期31卷 124-129页

作者： Wen-Jin Huang Mao-Fa Fang Xiong Xu Synergetic Innovation Center for Quantum Effects and Applications Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China School of Physics and Electronics Hunan Key Laboratory of Super Microstructure and Ultrafast ProcessState Key Laboratory of Powder MetallurgyCentral South UniversityChangsha 410083China

The protection of the entanglement between two V-atoms(EBTVA)in a multi-cavity coupling system is *** whole system consists of two *** two V-atoms are initially in the maximum entangled state and interacts locally with its own dissipative cavity which is coupled to the external cavities with high quality factor(ECWHQF).The results show that,when there is no ECWHQF,the EBTVA can be protected effectively in the case where the V-atom and the dissipative cavity are weak coupled in large detuning,while when there are different numbers n of ECWHQF coupled to two dissipative cavities,by adjusting the parameters of the number n of ECWHQF and the coupling strength k between cavities,the EBTVA can be protected perfectly and *** result provides an effective method for protecting entanglement resources of three-level system.

关键词： V-atom multi-cavity coupling system entanglement negativity

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Growth behaviors and emission properties of Co-deposited MAPbI_(3) ultrathin films on MoS_(2)

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Chinese Physics B 2023年第1期32卷 553-558页

作者：游思雯邵子依郭晓蒋俊杰刘金鑫王凯李明君欧阳方平邓楚芸宋飞孙家涛黄寒 Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics and ElectronicsCentral South UniversityChangsha 410083China College of Arts and Science National University of Defense TechnologyChangsha 410073China Key Laboratory of Interfacial Physics and Technology Shanghai Institute of Applied PhysicsChinese Academy of SciencesShanghai 201000China School of Information and Electronics MIIT Key Laboratory for Low-Dimensional Quantum Structure and DevicesBeijing Institute of TechnologyBeijing 100081China

Hybrid organic–inorganic perovskite thin films have attracted much attention in optoelectronic and information fields because of their intriguing properties. Due to quantum confinement effects, ultrathin films in nm scale usually show special properties. Here, we report on the growth of methylammonium lead iodide(MAPbI_(3)) ultrathin films via co-deposition of PbI_2 and CH_3NH_3I(MAI) on chemical-vapor-deposition-grown monolayer MoS_(2) as well as the corresponding photoluminescence(PL) properties at different growing stages. Atomic force microscopy and scanning electron microscopy measurements reveal the MoS_(2) tuned growth of MAPbI_(3) in a Stranski–Krastanov mode. PL and Kelvin probe force microscopy results confirm that MAPbI_(3) /MoS_(2) heterostructures have a type-Ⅱ energy level alignment at the interface. Temperaturedependent PL measurements on layered MAPbI_(3) (at the initial stage) and on MAPbI_(3) crystals in averaged size of 500 nm(at the later stage) show rather different temperature dependence as well as the phase transitions from tetragonal to orthorhombic at 120 and 150 K, respectively. Our findings are useful in fabricating MAPbI_(3) /transition-metal dichalcogenide based innovative devices for wider optoelectronic applications.

关键词： MAPbI_(3)/MoS_(2)heterostructure Co-deposition temperature-dependent photoluminescence growth behavior

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Exploring photon blockade in a two-photon Jaynes-Cummings model with atom and cavity drivings

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Physical Review A 2024年第4期110卷 043707页

作者： Hai-Ji Li Li-Bao Fan Shan Ma Jie-Qiao Liao Chuan-Cun Shu Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process and School of Physics School of Automation Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications

We explore a method for achieving photon blockade (PB) through a two-photon Jaynes-Cummings (JC) model that includes both cavity and atom drivings. Analytical expressions for the steady state are derived to calculate photon-number distribution and correlation functions. Based on this analysis, we establish the theoretical conditions required for generating PB by controlling both drivings and propose a scheme to identify conventional photon blockade (CPB) and unconventional photon blockade (UPB) by analyzing the second- and third-order correlation functions. We validate our findings through numerical simulations conducted in an artificial atom system. We discuss two cases, one in which the transition frequency of the two-level atom is in two-photon resonance with the cavity frequency and the other in which it is off-resonance. We observe a significant interplay between CPB and UPB effects in the resonant case. In the off-resonance case, we demonstrate that UPB can be achieved by manipulating the strengths of atom driving and cavity driving to satisfy a specific relationship while meeting the requirements for optimal detuning relations. This work provides essential insights into controlling the PB effect using the two-photon JC model with both the atom and cavity drivings.

关键词： Quantum control Quantum optics Single photon sources

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Giant thermoelectric effect governed by unique two-dimensional electronic structure and strong anharmonicity in layered nitrides

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Physical Review B 2024年第11期110卷 115202页

作者： Mengli Yao Min Li Long Zhang 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

Layered complex nitrides have emerged as a novel class of thermoelectric materials due to their unique geometrical and electronic structures. In this work, we employ density functional theory calculations combined with Boltzmann transport equation and thermal transport unified theory to explore the electrical and thermal transport properties and thermoelectric performance of layered nitrides AMN2 (A=Sr, Ba; M=Ti, Zr, Hf). It is found that the AMN2 family exhibits a large Seebeck coefficient and high power factor, ascribed to its multiband degeneracy and the presence of unique two-dimensional (2D) electronic structure. As the atomic mass of M increases, the lattice thermal conductivity κL decreases significantly. In particular, BaHfN2 demonstrates ultralow lattice thermal conductivity of 0.18 W/mK at room temperature. Even after accounting for both the particlelike propagation and wavelike phonon tunneling transport, ultralow κL is found across a wide temperature range. The ultralow κL is mainly attributed to the strong anharmonicity in BaHfN2 as reflected by the high phonon-phonon scattering rate and short phonon lifetime. Importantly, we find that p-type BaHfN2 exhibits a high figure of merit (ZT), achieving values of 2.19 at 300 K and 7.29 at 900 K, respectively. Additionally, through strain engineering, applying a moderate tensile stress of 0.5% remarkably increases the ZT of p-type increases to 2.58 at 300 K and reaches a maximum of 9.02 at 900 K, respectively. The present work unveils the importance of unique 2D electronic structures and strong anharmonicity induced by the weak-bonded heavy element on the thermoelectric performance, suggesting that the layered AMN2 family is a promising candidate for the development of high-performance thermoelectric devices.

关键词： Anharmonic lattice dynamics Electrical conductivity Electron-phonon coupling Electronic structure Optical phonons Phonons Scattering theory Seebeck effect Thermal conductivity Thermoelectric effects Thermoelectrics 3-dimensional systems Nitrides Two-dimensional electron gas Ab initio molecular dynamics Band structure methods Boltzmann theory Density functional calculations First-principles calculations Strain engineering

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