Superconductivity and unconventional density waves in vanadium-based kagome materials AV3Sb5

Recently, the discovery of vanadium-based kagome metal AV₃Sb₅ (A= K, Rb, Cs) has attracted great interest in the field of superconductivity due to the coexistence of superconductivity, non-trivial surface state and multiple density waves. In this topical review, we present recent works of superconductivity and unconventional density waves in vanadium-based kagome materials AV₃Sb₅. We start with the unconventional charge density waves, which are thought to correlate to the time-reversal symmetry-breaking orders and the unconventional anomalous Hall effects in AV₃Sb₅. Then we discuss the superconductivity and the topological band structure. Next, we review the competition between the superconductivity and charge density waves under different conditions of pressure, chemical doping, thickness, and strains. Finally, the experimental evidence of pseudogap pair density wave is discussed.     

ZrO2掺杂AZO防静电陶瓷的制备

以AZO陶瓷为基体,采用传统的固相烧结技术制备了ZrO2掺杂AZO防静电陶瓷,研究了不同烧结温度、ZrO2掺杂量对AZO陶瓷的表面电阻率、相对密度、维氏硬度的影响.通过XRD测定陶瓷的物相结构,SEM观察陶瓷的断面形貌,表面电阻测试仪测量陶瓷的表面电阻,维氏显微硬度仪测量陶瓷的维氏硬度,阿基米德排水法测量陶瓷密度等方法对ZrO2掺杂AZO陶瓷进行了分析表征.结果表明:当烧结温度为1450℃,ZrO2的掺杂量为1wt;时,其综合性能最佳.此时陶瓷表面电阻率为105Ω· cm,相对密度达97.61;,维氏硬度为357.5 HV0.3,已达到防静电陶瓷性能要求.     

Determination of the magnetic anisotropy constant of Cu/Fe/SiO2/Si by a magneto-optical Kerr effect susceptometer

The magneto-optical Kerr effect susceptometry technique is proposed to determine the uniaxial magnetic anisotropy(UMA) constant Ku. The magnetic properties of Cu/Fe/SiO2/Si grown by dc magnetron sputtering were investigated. The in-plane uniaxial magnetic anisotropy was probed by the magneto-optical Kerr effect(MOKE). The value of UMA, Ku= 2.5×103J/m3, was simulated from the field dependence of ac susceptibility along the hard axis according to the Stoner–Wohlfarth(S–W) model, which is consistent with Ku= 2.7×103J/m3 calculated from the magnetic hysteresis loops. Our results show that the magneto-optical Kerr effect susceptometry can be employed to determine the magnetic anisotropy constant owing to its high sensitivity.     

R~n上一类半线性椭圆方程解的存在唯一性和渐近性质

用上下解方法和位势估计，研究Rn上具有次线性项加超线性项半线性椭圆方程给出了其有界正解的存在性、唯一性和渐近性质，其中为常数，参数．     

Robustness of the unidirectional stripe order in the kagome superconductor CsV3Sb5

V-based kagome materials AV₃Sb₅ (A=K, Rb, Cs) have attracted much attention due to their novel properties such as unconventional superconductivity, giant anomalous Hall effect, charge density wave (CDW) and pair density wave. Except for the 2a₀×2a₀ CDW (charge density wave with in-plane 2×2 superlattice modulation) in AV₃Sb₅, an additional 1×4 (4a₀) unidirectional stripe order has been observed at the Sb surface of RbV₃Sb₅ and CsV₃Sb₅. However, the stability and electronic nature of the 4a₀ stripe order remain controversial and unclear. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we systematically study the 4a₀ stripe order on the Sb-terminated surface of CsV₃Sb₅. We find that the 4a₀ stripe order is visible in a large energy range. The STM images with positive and negative bias show contrast inversion, which is the hallmark for the Peierls-type CDW. In addition, below the critical temperature about 60 K, the 4a₀ stripe order keeps unaffected against the topmost Cs atoms, point defects, step edges and magnetic field up to 8 T. Our results provide experimental evidences on the existence of unidirectional CDW in CsV₃Sb₅.     

Pontrjagin空间上J.V.N代数的导子

本文证明Pontrjagin空间上非退化的J.V.N代数的导子是内的等价于它在该代数的奇异部分上 的限制为零.对退化的J.V.N代数,证明了Ⅱ1空间第0,Ⅱa和Ⅲa类J.V.N代数上的导子是内 的.通过构造例子说明了第Ⅰ,Ⅱb和Ⅲb类对称代数上的导子一般不是内的.     

JC~*-代数的抽象定义

本文给出JC~*-代数的抽象定义,并给出SC~*-代数是Π_k型的条件.     

Pontrjagin空间上一般算子代数弱闭和一致闭的等价条件

本文研究Pontrjagin空间上一般算子代数弱闭和一致闭的等价条件,得到定理:设C0(U),C1(U,L,R,D,V),C2a(U),C2b(U,R),C3a(U),C3b(U,R)分别是Ⅱk空间上第0,Ⅰ,Ⅱa,Ⅱb,Ⅲa和Ⅲb类的算子代数,则(1)C0(U),C2a(U)或C3a(U)为一致闭(弱闭)的等价条件是U是Hibert空间G上的C*-代数(W*-代数;(2)C1(U,L,R,D,V)为一致闭(弱闭)的等价条件是U是Hibert空间H上的C*-代数(W*-代数),并且R是闭子空间,V是闭算子,L对称闭的;(3)C2b(U,R)或C3b(U,R)为一致闭(弱闭)的等价条件是U是Hibert空间H上的C*-代数(W*-代数),并且R是闭子空间．     

不定度规空间的可测场

讨论了不定度规空间上的约化理论，引入了不定度规空间的可测场及其谐性的概念。给出了不定度规空间场是谐调可测场的充要条件以及谐调可测场的若干性质。     

磁性钴纳米晶的二维自组装

在两种表面活性剂存在下，采用高温醇还原，合成出单分散、平均颗粒尺寸为14±19nm，直径标准偏差小(～18%)的磁性金属Co纳米晶.利用x射线衍射、紫外吸收光谱、x射线光电子能谱及透射电子显微镜对其结构和表面价态进行了分析.并将磁性金属Co纳米晶自组织形成有序的二维(2D)六方紧密堆积结构. 关键词： Co纳米晶 单分散 自组装