Pandeya Ram Prakash, Pramanik Arindam, Sakhya Anup Pradhan, Mondal Rajib, Yadav A K, Jha S N, Thamizhavel A, Maiti Kalobaran
Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India.
Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
J Phys Condens Matter. 2021 Apr 21;33(19). doi: 10.1088/1361-648X/abe44c.
We investigate the evolution of the local structural parameters and their implication in unconventional superconductivity of 122 class of materials employing extended x-ray absorption fine structure studies. The spectral functions near the Fe- and As-absorption edges of CaFeAsand its superconducting composition, CaFeCoAs(= 12 K) exhibit evidence of enhancement of Fe contributions near the Fermi level with Co substitution, which becomes more prominent at low temperatures indicating enhanced role of Fe in the electronic properties with doping. As-Fe and Fe-Fe bondlengths derived from the experimental data reveal evolution with temperature across the magneto-structural transition in the parent compound. The evolution of these parameters in Co-doped superconducting composition is similar to its parent compound although no magneto-structural transition is observed in this system. These results reveal an evidence of doping induced evolution to the proximity to critical behavior and/or strong nematic fluctuations which might be important for superconductivity in this system.
我们利用扩展X射线吸收精细结构研究，研究了122类材料的局部结构参数的演变及其在非常规超导性中的意义。CaFeAs及其超导成分CaFeCoAs（= 12 K）的Fe和As吸收边附近的光谱函数显示，随着Co替代，费米能级附近Fe的贡献增强，这在低温下变得更加明显，表明Fe在掺杂后的电子性质中作用增强。从实验数据得出的As-Fe和Fe-Fe键长揭示了母体化合物中磁结构转变时随温度的演变。尽管在该系统中未观察到磁结构转变，但Co掺杂超导成分中这些参数的演变与其母体化合物相似。这些结果揭示了掺杂诱导的向临界行为和/或强向列涨落趋近的演变证据，这可能对该系统中的超导性很重要。
