In-plane electronic anisotropy of differently doped AFe2As2 (A = Ba, Eu) superconductors

将合成AFe2As2 （A=Ca, Ba, Eu）基材料和相关过渡金属化合物的单晶，其中电子相关强度和基态被调谐。具体来说，我们比较了Eu1-x KxFe2As2中的空穴掺杂对EuFe2(As1-xPx)2中的流体静力压力和化学压力的影响，特别强调了磁量子相变，超导性的出现及其与Eu2+局部矩的相互作用。在流体静压或化学加压的EuFe2As2中，低于20k的eu -矩的顺序导致超导性能的明显异常。此外，为了对铁-砷酸盐相对于铜酸盐和其他非常规超导体的电子相关强度进行分类，在（Ca,Ba）Fe2(As1-xSbx)2中施加负化学压力，使系统向更强的相关状态调整。此外，通过空穴掺杂将同结构小带隙绝缘体和反铁磁体BaMn2As2调谐到金属态。我们的单晶通过输运，磁性和热力学探针，以及光学和远红外光谱，角分辨光发射光谱，电子自旋共振和其他技术进行了研究。

Single crystals of AFe2As2 (A=Ca, Ba, Eu) based materials and related transition metal pnictides will be synthesized, in which the strength of electronic correlations and the ground state is tuned. Specifically, we compare the effects of hole doping in Eu1-x KxFe2As2 with hydrostatic as well as chemical pressure in EuFe2(As1-xPx)2 with particular emphasis on the magnetic quantum phase transition, the emergence of superconductivity and its interplay with Eu2+ local moments. In hydrostatically or chemically pressurized EuFe2As2, the ordering of Eu-moments below 20 K leads to distinct anomalies in the superconducting properties. Additionally, in order to classify the strength of electronic correlations of iron-arsenites with respect to the cuprates and other unconventional superconductors, negative chemical pressure is applied in (Ca,Ba)Fe2(As1-xSbx)2 to tune the system towards the stronger correlated state. Furthermore, the isostructural small-bandgap insulator and antiferromagnet BaMn2As2 is tuned towards the metallic state by hole doping. Our single crystals are investigated by transport, magnetic and thermodynamic probes, as well as within collaborations by optical- and far-infrared spectroscopy, angular-resolved photo-emission spectroscopy, electron-spin resonance and further techniques.