Hedgehog Spin-Vortex Crystal Antiferromagnetic Quantum Criticality in CaK (Fe1-xNix)4As4 Revealed by NMR

Ding, Q.-P. and Meier, W.R. and Cui, J. and Xu, M. and Böhmer, A.E. and Bud'Ko, S.L. and Canfield, P.C. and Furukawa, Y.

Volume: 121 Pages:
DOI: 10.1103/PhysRevLett.121.137204
Published: 2018

Two ordering states, antiferromagnetism and nematicity, have been observed in most iron-based superconductors (SCs). In contrast to those SCs, the newly discovered SC CaK(Fe1-xNix)4As4 exhibits an antiferromagnetic (AFM) state, called hedgehog spin-vortex crystal (SVC) structure, without nematic order, providing the opportunity for the investigation into the relationship between spin fluctuations and SC without any effects of nematic fluctuations. Our As75 nuclear magnetic resonance studies on CaK(Fe1-xNix)4As4 (0≤x≤0.049) revealed that CaKFe4As4 is located close to a hidden hedgehog SVC AFM quantum-critical point (QCP). The magnetic QCP without nematicity in CaK(Fe1-xNix)4As4 highlights the close connection of spin fluctuations and superconductivity in iron-based SCs. The advantage of stoichiometric composition also makes CaKFe4As4 an ideal platform for further detailed investigation of the relationship between magnetic QCP and superconductivity in iron-based SCs without disorder effects. © 2018 American Physical Society.

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