Superconducting and normal-state properties of APd2As2 (A = Ca, Sr, Ba) single crystals
Superconducting and normal-state properties of APd2As2 (A = Ca, Sr, Ba) single crystals
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DOI：
10.1103/physrevb.87.224510
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发表时间：
2013-06-20
影响因子：
3.7
通讯作者：
Johnston, D. C.
中科院分区：
文献类型：
--
作者：
Anand, V. K.;Kim, H.;Johnston, D. C.
报道了Ad(2)As(2)(A=Ca，Sr，Ba)单晶的合成和晶体结构、磁化率X、磁化强度M、比热C-p、面内电阻率Rho和面内磁穿透深度随温度T和磁场H的变化。CaPd2As2和SrPd2As2结晶为塌陷的体心四方ThCr2Si2型结构(I4/mmm)，而BaPd2As2结晶为原始的四方CeMg2Si2型结构(P4/mmm)，与文献数据一致。Rho(T)数据显示了所有三种化合物的金属行为。在T-c=1.27和0.92K以下，CaPd2As2和SrPd2As2分别具有超导电性，而BaPd2As2只有少量的超导电性。没有观察到其他相变。X_i(T)和M(H)数据揭示了正常状态下的各向异性抗磁性，CaPd_2As_2和BaPd_2As_2的X_i(C)和Gt；X_i(Ab)，以及SrPd_2As_2的X_i(C)和L_t；X_i(B)。正常态和超导态数据表明，CaPd2As2和SrPd2As2是传统的II型无节S波电声子超导体。利用我们最近提出的超导理论的α模型，分析了CaPd_2As_2的电子超导态热容数据，指出该化合物的S带隙在动量空间中是各向异性的。
The synthesis and crystallography, magnetic susceptibility chi, magnetization M, specific heat C-p, in-plane electrical resistivity rho, and in-plane magnetic penetration depth measurements are reported for single crystals of APd(2)As(2) (A = Ca, Sr, Ba) versus temperature T and magnetic field H. The crystals were grown using PdAs self-flux. CaPd2As2 and SrPd2As2 crystallize in a collapsed body-centered tetragonal ThCr2Si2-type structure (I4/mmm), whereas BaPd2As2 crystallizes in the primitive tetragonal CeMg2Si2-type structure (P4/mmm), in agreement with literature data. The rho(T) data exhibit metallic behavior for all three compounds. Bulk superconductivity is reported for CaPd2As2 and SrPd2As2 below T-c = 1.27 and 0.92 K, respectively, whereas only a trace of superconductivity is found in BaPd2As2. No other phase transitions were observed. The chi(T) and M(H) data reveal anisotropic diamagnetism in the normal state, with chi(c) > chi(ab) for CaPd2As2 and BaPd2As2, and chi(c) < chi(ab) for SrPd2As2. The normal and superconducting state data indicate that CaPd2As2 and SrPd2As2 are conventional type-II nodeless s-wave electron-phonon superconductors. The electronic superconducting state heat capacity data for CaPd2As2, which has an extremely sharp heat capacity jump at T-c, are analyzed using our recent elaboration of the alpha-model of the BCS theory of superconductivity, which indicates that the s-wave gap in this compound is anisotropic in momentum space.