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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 106-111页

作者： Yuhang Zhang Cong Liu xiyu zhu Hai-Hu Wen Center for Superconducting Physics and Materials National Laboratory of Solid State Microstructures and Department of PhysicsNational Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China

Recent claim of discovering above-room-temperature superconductivity(Tc≈400 K)at ambient pressure in copper doped apatite Pb10(PO_(4))_(6)O has stimulated world-wide enthusiasm and impulse of motion.A lot of follow-up works have been carried out with controversial *** check whether superconductivity is really present or absent in the material,we need samples which should have a rather pure phase of Pb_(10-x)Cux(PO_(4))_(6)*** we report the characterization results from the Pb_(10-x)Cux(PO_(4))_(6)O with a fraction of about 97 wt.%inferred from the fitting to the X-ray diffraction pattern,if assuming Cu2S as the only *** resistivity measurements show that it is a semiconductor characterized roughly by a ln(1/T)temperature dependence in wide temperature region without trace of *** measurements show that it has a general ferromagnetic signal with a weak superparamagnetic *** grains of the sample show clear interactions with a Nb Fe B *** detected Cu concentration is much lower than the expected nominal *** results show the absence of metallicity and superconductivity in Pb_(10-x)Cux(PO_(4))_(6)O at ambient pressure,and suggest the presence of strong correlation effect.

关键词： superconductivity Pb10(PO4)6O ferromagnetic correlation effect

Pressure-induced color change arising from transformation between intra-and inter-band transitions in LuH_(2±x)N_(y)

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Science China(Physics,Mechanics & Astronomy) 2024年第2期67卷 161-166页

作者： Zhe Liu Yingjie Zhang Shenyang Huang Xue Ming Qing Li Chenghao Pan Yaomin Dai Xiaoxiang Zhou xiyu zhu Hugen Yan Hai-Hu Wen Center for Superconducting Physics and Materials National Laboratory of Solid State Microstructures and Department of PhysicsNational Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China State Key Laboratory of Surface Physics Key Laboratory of Micro and Nano-Photonic Structures of the Ministry of EducationDepartment of PhysicsFudan UniversityShanghai 200433China

The pressure-induced color change in the nitrogen-doped lutetium hydride has triggered extensive discussions about the underlying physics and potential ***,we study the optical response of LuH_(2±x)N_(y)in a broad frequency range at ambient pressure and its evolution with pressure in the visible spectral *** broad-band optical spectra at ambient pressure reveal a Drude component associated with intra-band electronic transitions and two Lorentz components(L1 and L2)arising from inter-band electronic *** application of pressure causes a spectral weight transfer from L1 to the Drude component,leading to a blue shift of the plasma edge in the reflectivity spectrum alongside a reduction of the high-frequency *** results suggest that the pressure-induced color change in LuH_(2±x)N_(y)is closely related to the transformation between intra-and inter-band electronic transitions,providing new insights into the mechanism of the pressure-induced color change in LuH_(2±x)N_(y).

关键词： nitrogen-doped lutetium hydride optical spectroscopy high-pressure technique color change

企业数字化转型与投资效率--来自年报文本的经验证据

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经济科学 2024年第4期 93-113页

作者：朱茜俣谭小芬北京大学光华管理学院北京航空航天大学经济管理学院

本文利用2007—2022年A股上市公司的财报数据,采用词频统计的方式定义了企业的数字化转型程度。研究发现:企业数字化转型能够显著降低企业的非效率投资;基于PSM-DID检验发现,2014年“两化融合”试点企业在政策出台之后投资效率提升较多... 详细信息

本文利用2007—2022年A股上市公司的财报数据,采用词频统计的方式定义了企业的数字化转型程度。研究发现:企业数字化转型能够显著降低企业的非效率投资;基于PSM-DID检验发现,2014年“两化融合”试点企业在政策出台之后投资效率提升较多。企业数字化转型主要通过改善公司治理的内部渠道和提升公司股票信息监督的外部渠道来提高投资效率。数字化转型对投资效率的提升作用在融资约束更低、年报可读性更低、行业集中度更高的企业中表现得更为明显。此外,数字化转型还可以增加数字化研发投入和专利数目,提升经营表现。

关键词：数字化转型投资效率公司治理股票信息

Signature of Superconductivity in Pressurized La_(4)Ni_(3)O_(10)

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Chinese Physics Letters 2024年第1期41卷 77-84页

作者：李庆张英杰项浙宁张宇航祝熙宇闻海虎 National Laboratory of Solid State Microstructures and Department of Physics Center for Superconducting Physics and MaterialsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China

The discovery of high-temperature superconductivity near 80K in bilayer nickelate La_(3)Ni_(2)O_(7)under high pressures has renewed the exploration of superconducting nickelate in bulk *** extension of superconductivity in other nickelates in a broader family is also ***,we report the experimental observation of superconducting signature in trilayer nickelate La_(4)Ni_(3)O_(10)under high *** using a modified solgel method and post-annealing treatment under high oxygen pressure,we successfully obtained polycrystalline La_(4)Ni_(3)O_(10)samples with different transport behaviors at ambient *** we performed high-pressure electrical resistance measurements on these samples in a diamond-anvil-cell ***,the signature of possible superconducting transition with a maximum transition temperature(T_(c))of about 20K under high pressures is observed,as evidenced by a clear drop of resistance and the suppression of resistance drops under magnetic *** the resistance drop is sample-dependent and relatively small,it appears in all of our measured *** argue that the observed superconducting signal is most likely to originate from the main phase of La_(4)Ni_(3)O_(10).Our findings will motivate the exploration of superconductivity in a broader family of nickelates and shed light on the understanding of the underlying mechanisms of high-T_(c) superconductivity in nickelates.

关键词： materials superconductivity signature

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积石山6.2级地震村镇民居震害调研与分析

地震工程与工程振动 2024年第3期44卷 200-213页

作者：兰官奇陈涛代建波朱熹育孙杲辰西安石油大学土木工程学院陕西西安710065

探明积石山6.2级地震中村镇民居的震害情况,归纳总结了灾区村镇民居的主要结构特征、建造习惯和施工工艺,分析了不同结构形式村镇民居的倒塌情况和典型震害特征,评析了传统建造习惯对民居抗震防灾能力的影响。结果表明:民居结构体系多... 详细信息

探明积石山6.2级地震中村镇民居的震害情况,归纳总结了灾区村镇民居的主要结构特征、建造习惯和施工工艺,分析了不同结构形式村镇民居的倒塌情况和典型震害特征,评析了传统建造习惯对民居抗震防灾能力的影响。结果表明:民居结构体系多为“虎抱头”式砖木结构房屋,占调研总数的50.9%,生土结构和砖混结构较少,分别占调研总数的28.2%、20.9%;调研区域内大量生土结构民居发生整体倒塌,砖木结构民居出现整体倒塌案例较少,砖混结构未发现整体倒塌案例;砖木结构民居震害主要表现为山墙转角开裂、梁柱节点处脱榫、局部山墙倒塌、屋盖搭接处开裂,生土结构民居震害主要表现为山墙转角破损、山墙歪闪倒塌和屋盖塌陷,砖混结构民居震害主要表现为墙体开裂、歪闪倒塌和楼(屋)盖破坏;泥浆砌墙、厚覆黄土屋盖、大重量门盖装饰等不良建造习惯加剧了民居的震害,在后续恢复重建工作中应予以改进。针对不同结构体系震害特征和建造习惯提出了提高村镇民居抗震防灾能力的措施和建议,以期为灾区村镇民居的建设、加固改造提供参考。

关键词：积石山地震震害调查村镇民居砖木结构建造习惯

Contrasting physical properties of the trilayer nickelates Nd4Ni3O10 and Nd4Ni3O8

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Science China(Physics,Mechanics & Astronomy) 2021年第2期64卷 98-104页

作者： Qing Li ChengPing He xiyu zhu Jin Si XinWei Fan Hai-Hu Wen Center for Superconducting Physics and Materials National Laboratory of Solid State Microstructures and Department of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing210093China

We report the crystal structures and physical properties of trilayer nickelates Nd4Ni3O10and *** of magnetization and electrical resistivity display contrasting behaviors in the two ***4Ni3O10shows a paramagnetic metallic behavior with a metal-to-metal phase transition(T^*)at about 162 K,as revealed by both magnetic susceptibility and *** magnetoresistance and Hall coefficient results show a negative magnetoresistance at low temperatures and the carrier type of Nd4Ni3O10is dominated by hole-type charge *** significant enhancement of Hall coefficient and resistivity below T*suggests that effective charge carrier density decreases when cooling through the transition *** contrast,Nd4Ni3O8 shows an insulating *** addition,this compound shows a paramagnetic behavior with the similar magnetic moment as that of Nd4Ni3O10derived from the Curie-Weiss *** may suggest that the magnetic moments in both systems are contributed by Nd^3+ *** applying pressures up to about 49 GPa,the insulating behavior is still present and becomes even stronger under a high *** results suggest that the different Ni configurations(Ni^1+/2+ or Ni^2+/3+)and the changes of coordination environment of Ni sites may account for the contrasting behaviors in trilayer nickelates Nd4Ni3O10and Nd4Ni3O8.

关键词： trilayer nickelate Nd4Ni3O10 and Nd4Ni3O8 high-pressure study

Superconductivity in Li OHFe S single crystals with a shrunk c-axis lattice constant

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Science China(Physics,Mechanics & Astronomy) 2017年第2期Mechanics & Astronomy) .卷 50-54页

作者： Hai Lin Rui Zhe Kang Lu Kong xiyu zhu Hai-Hu Wen Center for Superconducting Physics and Materials National Laboratory of Solid State Microstructures and Department of PhysicsNational Collaborative Innovation Center of Advanced Microstructures Nanjing University

By using a hydrothermal ion-exchange method, we have successfully grown superconducting crystals of Li OHFe S with Tcof about 2.8 K. Being different from the sister sample(Li1-xFex)OHFe Se, the energy dispersion spectrum analysis on Li OHFe S shows that the Fe/S ratio is very close to 1:1, suggesting an almost charge neutrality and less electron doping in the Fe S planes of the system. Comparing with the non superconducting Li OHFe S crystal, each peak of the X-ray diffraction pattern of the superconducting crystal splits into two, and the diffraction peaks locating at lower reflection angles are consistent with that of non-superconducting ones. The rest set of diffraction peaks with higher reflection angles is corresponding to the superconducting phase, suggesting that the superconducting phase may has a shrunk c-axis lattice constant. Magnetization measurements indicate that the magnetic shielding due to superconductivity can be quite high under a weak magnetic field. The resistivity measurements under various magnetic fields show that the upper critical field is quite low, which is similar to the tetragonal Fe S superconductor.

关键词： iron chalcogenides magnetic properties transport properties

Growth and transport properties of CaFeAsF_(1-x) single crystals

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Science China(Physics,Mechanics & Astronomy) 2014年第4期57卷 632-636页

作者： TAO Jian LI Sheng zhu xiyu YANG Huan WEN HaiHu Center for Superconducting Physics and Materials National Laboratory of Solid State Microstructures and Department of PhysicsNanjing University

Using self-flux method,we have successfully grown the parent phase of the single crystals of *** X-ray di?raction indicates good ***-plane resistivity shows a bad metallic behavior with a sharp drop of resistivity at about T SDW=*** anomaly is associated with the possible spin density wave(SDW)*** near T SDW,the resistivity exhibits a cusp-like feature,which may be understood as the strong coupling effect between the electrons and the antiferromagnetic(AF)spin fluctuations.A reduction of fluorine or application of a high pressure will suppress the SDW feature and induce *** effect measurements reveal a positive Hall coefficient below T SDW indicating a dominant role of the hole-like charge carriers in the parent *** magnetoresistance has been observed below T SDW suggesting multiple conduction channels of the charge carriers.

关键词： CaFeAsF 1-x single crystal antiferromagnetic spin order multiple conduction channels

Discovery of a new nontoxic cuprate superconducting system Ga-Ba-Ca-Cu-O

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Science China(Physics,Mechanics & Astronomy) 2018年第9期61卷 82-85页

作者： Yue Zhang Wenhao Liu Jin Si xiyu zhu Chengping He Haonan Zhao Hai-Hu Wen Center for Superconducting Physics and Materials National Laboratory of Solid State Microstructures and Department of PhysicsNational Collaborative Innovation Center of Advanced Microstructures Nanjing University

Superconductivity is observed in a new nontoxic cuprate system Ga-Ba-Ca-Cu-O,with T_c=82 K for Ga Ba_2Ca_5Cu_6O_(14+δ)(Ga-1256)and T_c=116 K probably for Ga Ba_2Ca_3Cu_4O_(10+δ)(Ga-1234)or Ga Ba_2Ca_2Cu_3O_(8+δ)(Ga-1223),*** compounds are fabricated by solid state reaction method under high pressure and high *** are characterized by resistivity,magnetization and X-ray diffraction(XRD)*** temperature dependence of magnetization measured in both zero-field-cooled and field-cooled processes on one sample(S1)shows two superconducting transitions at about 82 K and113 *** estimated shielding fraction for the phase with T_cof 82 K is about 67%,while the fraction for another phase with T_(c )of 113 K is quite *** XRD Rietveld refinement for S1 indicates two main phases existing in the sample,Ga-1256 with fraction of about 58%and non-superconducting Ca_(0.85)Cu O_2with fraction of about 42%***,we can conclude the superconducting phase with transition temperature of 82 K is due to *** resistivity measurement also confirms the superconductivity for S1,and the resistivity reaches zero at about 82 *** temperature dependence of magnetization for another sample(S2)shows much higher superconducting shielding fraction for the phase with T_cof 116 K,which may be a promising prospective for the synthesis of Ga-1234 or Ga-1223 phase.

关键词： cuprates high pressure and high temperature superconductivity

Structural and transport properties of Sr_2VO_(3-δ)FeAs superconductors with different oxygen deficiencies

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Science China(Physics,Mechanics & Astronomy) 2010年第7期53卷 1202-1206页

作者： HAN Fei zhu xiyu MU Gang CHENG Peng SHEN Bing ZENG Bin WEN HaiHu National Laboratory for Superconductivity Institute of Physics and Beijing National Laboratory for Condensed Matter PhysicsChinese Academy of SciencesBeijing 100190China

Sr2VO3-δFeAs superconductors with different oxygen deficiencies have been successfully *** is found that the superconducting transition temperature drops down monotonically with the increase of nominal oxygen *** diminishing of superconductivity is accompanied by the enhancement of residual resistivity,indicating an anomalous scattering effect induced by the oxygen *** highest superconducting transition temperature at about 36 K is achieved near the stoichiometrical sample *** Hall effect measurements reveal that the density of charge carriers(electron-like here) varies qualitatively with the increase of nominal oxygen *** measurements show that the superconducting transition changes from one-step-like shape at low fields to two-step-like one at high fields,indicating an enhanced vortex motion due to the high anisotropy.

关键词： iron-based superconductor oxygen deficiency transport properties high anisotropy