Evolution of local structure and superconductivity in CaFe2As2

Ram Prakash Pandeya; Arindam Pramanik; Anup Pradhan Sakhya; Rajib Mondal; A K Yadav; S N Jha; A Thamizhavel; Kalobaran Maiti

doi:10.1088/1361-648X/abe44c

Evolution of local structure and superconductivity in CaFe₂As₂

J Phys Condens Matter. 2021 Apr 21;33(19). doi: 10.1088/1361-648X/abe44c.

Authors

Ram Prakash Pandeya¹, Arindam Pramanik¹, Anup Pradhan Sakhya¹, Rajib Mondal¹, A K Yadav², S N Jha², A Thamizhavel¹, Kalobaran Maiti¹

Affiliations

¹ Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India.
² Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.

PMID: 33556927
DOI: 10.1088/1361-648X/abe44c

Abstract

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 FeK- and AsK-absorption edges of CaFe₂As₂and its superconducting composition, CaFe_1.9Co_0.1As₂(T_c= 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.

Keywords: EXAFS; EXANES; Fe-based superconductors; magnetic transition; structural transition; unconventional superconductivity.