Superconductivity in Hole-Doped （S1-xKx）Fe2As2

A series of layered （Sr1-xKx）Fe2As2 compounds with nominal x = 0-0.40 are synthesized by solid state reaction method. Similar to other parent compounds of iron-based pnictide superconductors, pure SrFe2As2 shows a strong resistivity anomaly near 210 K, which was ascribed to the spin-density-wave instability. The anomaly temperature is much higher than those observed in LaOFeAs and BaFe2As2, the two prototype parent compounds with ZrCuSiAs- and ThCr2Si2-type structures. K-doping strongly suppresses this anomaly and induces superconductivity. Like in the case of K-doped BaFe2As2, sharp superconducting transitions at Tc ～ 38 K is observed. We perform the Hall coefficient measurement, and confirm that the dominant carriers are hole-type. The carrier density is enhanced by a factor of 3 in comparison to F-doped LaOFeAs superconductor.     

高效液相色谱-串联质谱法对家畜尿液中苯乙醇胺A残留检测研究

建立了高效液相色谱-串联质谱(HPLC-MS/MS)检测猪尿、牛尿和羊尿中苯乙醇胺A残留的方法。尿液经酶解、加入内标物、乙酸乙酯萃取、MCX固相萃取柱净化后,供HPLC-MS/MS检测。采用电喷雾离子源正模式,在多反应检测(MRM)模式下分析,苯乙醇胺A定性离子对分别为m/z 345/150和345/327,定量离子对为m/z 345/327;苯乙醇胺A内标物定性离子对为m/z 348/330,定量离子对为m/z 348/330。苯乙醇胺A含量在0～50.0μg/L范围内的线性关系良好(R2=0.9990);检出限为0.03μg/L,定量限为0.1μg/L。在猪尿、牛尿和羊尿中的回收率分别78.4%～82.9%,85.7%～93.3%和79.8%～84.9%;相对标准偏差分别为0.8%～4.2%,1.6%～5.6%和2.9%～5.8%。     

Magnetic phase transitions and large mass enhancement in single crystal CaFe4As3

High quality single crystal CaFe₄ As₃ was grown by using the Sn flux method. Unlike layered CaFe₂ As₂ , CaFe₄ As₃ crystallizes in an orthorhombic three-dimensional structure. Two magnetic ordering transitions are observed at ～ 90 K and ～ 27 K, respectively. The high temperature transition is an antiferromagnetic（AF） ordering transition. However, the low temperature transition shows complex properties. It shows a ferromagnetic-like transition when a field is applied along b-axis, while antiferromagnetism-like transition when a field is applied perpendicular to b-axis. These results suggest that the low temperature transition at 27 K is a first-order transition from an AF state to a canted AF state. In addition, the low temperature electron specific heat coefficient reaches as high as 143 mJ/mol·K 2 , showing a heavy fermion behavior.     

Tri-hexagonal charge order in kagome metal CsV3Sb5 revealed by 121Sb nuclear quadrupole resonance

We report ¹²¹Sb nuclear quadrupole resonance(NQR)measurements on kagome superconductor CsV₃Sb₅ with Tc=2.5 K.¹²¹Sb NQR spectra split after a charge density wave(CDW)transition at 94 K,which demonstrates a commensurate CDW state.The coexistence of the high temperature phase and the CDW phase between 91 K and 94 K manifests that it is a first order phase transition.The CDW order exhibits tri-hexagonal deformation with a lateral shift between the adjacent kagome layers,which is consistent with 2×2×2 superlattice modulation.The superconducting state coexists with CDW order and shows a conventional s-wave behavior in the bulk state.     

被动电磁装甲非线性力承载分析的力学、数学模型

电磁装甲技术是一项崭新的军用技术，目前，世界上许多军事强国的研究机构已经在积极地开展理论研究和缩比实验，并取得了很多的研究成果。在本文中，作者首次明确地提出了应用电磁力理论原理分析电磁装甲的问题。利用电磁学的理论建立了被动电磁装甲(PEMA)数学计算模型；以穿甲弹的穿甲杆为例，借助功能强大的有限元分析法，推导了采用能量法将分布力转化为集中力的求解过程。这一推导过程经过变形后同样适用于对金属射流作用原理的分析。     

拉伸状态NbSe3在纵向磁场下的负磁阻效应

本文研究了准一维电荷密度波材料ＮｂＳｅ３晶须自然状态（ε＝０）和受到拉伸的状态（ε＞０）下在纵向磁场中的磁阻效应．温度Ｔ≤５０Ｋ时，无论自然状态还是拉伸状态（ε＝１．５％）都没有观察到负磁阻．但是，当温度升高到Ｔ＝７０Ｋ，我们观察到ＮｂＳｅ３晶须受到拉伸至ε＝１．５％时有负磁阻效应；进一步增大ε至１．８％，负磁阻效应更明显；不拉伸（ε＝０）则没有磁阻．文中就这个现象进行了讨论．     

Novel Atomic Mirror with a Blue—Detuned Semi—Gaussian Beam

A novel and simple atomic mirror composed of a blue-detuned semi-Gaussian beam is proposed.From the Fresnel diffraction theory,the intensity distributions of a collimated Gaussian laser beam diffracted by the straight edge of a semi-infinite opaque plate are studied.The optical potential of the semi-Gaussian beam for 85Rb atoms and its spontaneous emission probability are calculated and compared with the performance of the evanescent-wave mirror.Our study shows that the blue-detuned semi-Gaussian beam,as a novel atomic mirror,can be used to reflect atomic beam efficiently,and under the same beam parameters and lower normal atomic velocity,the performance of the semi-Gaussian-beam mirror is better than that of the evanescent-wave mirror.     

Crystal growth,structural and physical properties of the 5d noncentrosymmetric LaOsSi_3

LaOsSi3 single crystals are synthesized for the first time by an arc melting method. The crystal features a tetrag- onal BaNiSn3-type structure （space group 14mm） which lacks inversion symmetry along the crystallographic c axis and is isostructural with the intensively studied Rashba-type noncentrosymmetric superconductors LaRhSi3 and LaIrSi3. Un- like LaRhSi3 and LaIrSi3 displaying superconductivity, LaOsSi3 shows only metallic behavior over the measured temper- ature range of 2 K-300 K. The Sommerfeld coefficient ]/derived from specific heat is 5.76 mJ.mol-1 -K-2, indicating that LaOsSi3 has a weak electronic correlation effect. The absence of superconductivity in LaOsSi3 may lie in the Os 5d bands in the electronic structure. If it is true, it would be useful to provide complementary knowledge in understanding the relation between conduction and the d bands of M in LaMSi3 compounds （M = transition metals）.     

Sr2RuO4正常态的c方向的磁阻的研究

研究了典型的层状钙钛矿结构超导单晶Sr₂RuO₄在c方向的磁阻(Δρ/ρ₀)(H∥ab,J∥c)的变化.实验发现,磁阻表现出强烈的各向异性,并且随着温度T的降低,磁阻效应越明显;当在平面ab内旋转磁场H的方向时,磁阻成周期性变化;实验表明,磁场沿(110)方向时,出现磁阻的极大值.分别从Sr₂RuO₄的费米面的各向异性、载流子散射率、c方向能带色散的各向异性等方面来解释这些输运性质. 关键词： 2RuO₄')" href="#">Sr₂RuO₄ 磁阻     

Sr_2RuO_4正常态的c方向的磁阻的研究

研究了典型的层状钙钛矿结构超导单晶Sr2RuO4在c方向的磁阻(Δρ/ρ0)(H∥ab,J∥c)的变化.实验发现,磁阻表现出强烈的各向异性,并且随着温度T的降低,磁阻效应越明显;当在平面ab内旋转磁场H的方向时,磁阻成周期性变化;实验表明,磁场沿(110)方向时,出现磁阻的极大值.分别从Sr2RuO4的费米面的各向异性、载流子散射率、c方向能带色散的各向异性等方面来解释这些输运性质.