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TT: Fachverband Tiefe Temperaturen

TT 34: Fe-based Superconductors

TT 34.3: Talk

Wednesday, March 29, 2023, 12:00–12:15, HSZ 103

Superconductivity of CaKFe₄As₄ under anisotropic strains — B. Zúñiga Céspedes¹, A. Valadkhani², S. Mandloi¹, M. Xu^3,4, J. Schmidt^3,4, S. L. Bud’ko^3,4, P. C. Canfield^3,4, A. P. Mackenzie^1,5, R. Valentí², and •E. Gati¹ — ¹MPI CPfS, 01187 Dresden, DE — ²Inst. for Theor. Physics, Goethe University, 60438 FFM, DE — ³Ames Lab, US DOE, Ames, IA 50011, USA — ⁴Dept. of Physics and Astronomy, Iowa State Uni, Ames, IA 50011, USA — ⁵Scottish Universities Physics Alliance, School of Physics and Astronomy, Uni of St Andrews, UK

CaKFe₄As₄ is an exceptional member of the family of Fe-based superconductors. First, it is a stochiometric superconductor at ambient pressure with high critical temperature T_c ∼ 35 K. Second, this superconducting phase can be found in close proximity to a so-called hedgehog vortex magnetic order (SVC), which does preserve tetragonal symmetry. This is in contrast to the ubiquitous stripe-type magnetic order (SSDW) in the Fe-based superconductors that is accompanied by a vestigial nematic phase. Thus, CaKFe₄As₄ is an important testbed to investigate the interplay of superconductivity with different magnetic orders and nematicity. Here, we will discuss the impact of anisotropic strains, which couple directly to the nematic order parameter, on superconductivity. To this end, we present measurements of T_c as well as results of DFT calculations of the stability of SVC vs. SSDW order under large strains. Our results support the notion that nematic fluctuations contribute to superconducting pairing in this high-T_c superconductor.Funded through the SFB/TRR288 (Elasto-Q-mat).