单晶SrCo2As2的晶体学、电学、热学和磁学性质
Crystallographic, Electronic, Thermal and Magnetic Properties of Single-Crystal SrCo2As2
摘要：
非弹性中子散射测量结果表明，在温度T = 5 K [W. Jayasekara等人，arXiv：1306.5174]中发现，它们与高温超导体的同质结构的AFe_2As_2（A = Ca，Sr，Ba）母体化合物相同。这一令人惊讶的发现表明SrCo2As2也可能是高Tc超导性的良好母体化合物。在这里，结构和热膨胀，电阻率ρ，角分辨光电子能谱（ARPES），热容Cp，磁化率chi，75 As NMR和中子衍射测量SrCo 2 As 2晶体一起报告LDA能带结构计算，进一步阐明了这个迷人的材料。c轴热膨胀系数α_c在7至300 K范围内为负，而α_a在该T范围内为正。ρ（T）显示金属特性。ARPES测量和能带理论证实了金属的性质，并在费米能级E_F附近发现了一个平坦的能带。能带计算显示出由平坦的d_{x^2 - y^2}能带引起的态密度D（E_F）的一个非常尖锐的峰。索末菲系数的电子比热与chi（T = 0）的比较表明存在强铁磁性巡回自旋相关性的基础上的斯通纳标准预测，SrCo2As2应该是一个巡回铁磁体，在冲突的磁化数据。的chi（T）确实有一个大的幅度，但也表现出广泛的最大值在115 K的动态短程原子力显微镜自旋相关的暗示，与中子散射数据。测量结果表明，在1.3和300 K之间没有任何类型的相变的证据，我们建议，金属SrCo_2As_2具有无隙量子自旋液体基态。
英文摘要：
In tetragonal SrCo2As2 single crystals, inelastic neutron scattering measurements demonstrated that strong stripe-type antiferromagnetic (AFM) correlations occur at a temperature T = 5 K [W. Jayasekara et al., arXiv:1306.5174] that are the same as in the isostructural AFe2As2 (A = Ca, Sr, Ba) parent compounds of high-Tc superconductors. This surprising discovery suggests that SrCo2As2 may also be a good parent compound for high-Tc superconductivity. Here, structural and thermal expansion, electrical resistivity rho, angle-resolved photoemission spectroscopy (ARPES), heat capacity Cp, magnetic susceptibility chi, 75As NMR and neutron diffraction measurements of SrCo2As2 crystals are reported together with LDA band structure calculations that shed further light on this fascinating material. The c-axis thermal expansion coefficient alpha_c is negative from 7 to 300 K, whereas alpha_a is positive over this T range. The rho(T) shows metallic character. The ARPES measurements and band theory confirm the metallic character and in addition show the presence of a flat band near the Fermi energy E_F. The band calculations exhibit an extremely sharp peak in the density of states D(E_F) arising from a flat d_{x^2 - y^2} band. A comparison of the Sommerfeld coefficient of the electronic specific heat with chi(T = 0) suggests the presence of strong ferromagnetic itinerant spin correlations which on the basis of the Stoner criterion predicts that SrCo2As2 should be an itinerant ferromagnet, in conflict with the magnetization data. The chi(T) does have a large magnitude, but also exhibits a broad maximum at 115 K suggestive of dynamic short-range AFM spin correlations, in agreement with the neutron scattering data. The measurements show no evidence for any type of phase transition between 1.3 and 300 K and we propose that metallic SrCo2As2 has a gapless quantum spin-liquid ground state.
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