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arXiv · 1503.08298

Nearly-critical spin and charge fluctuations in KFe2As2 observed by high-pressure NMR

P. S. Wang·P. Zhou·J. Dai·J. Zhang·X. X. Ding·H. Lin·H. H. Wen·B. Normand·R. Yu·Weiqiang Yu
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Abstract

We report a high-pressure 75As NMR study on the heavily hole-doped iron pnictide superconductor KFe2As2 (Tc~3.8 K). The low-energy spin fluctuations are found to decrease with applied pressure up to 2 GPa, but then increase again, changing in lockstep with the pressure-induced evolution of Tc. Their diverging nature suggests close proximity to a magnetic quantum critical point at a negative pressure of P~-0.6 GPa. Above 2.4 GPa, the 75As satellite spectra split below 40 K, indicating a breaking of As site symmetry and an incipient charge order. These pressure-controlled phenomena demonstrate the presence of nearly-critical fluctuations in both spin and charge, providing essential input for the origin of superconductivity.

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P. S. Wang, P. Zhou, J. Dai, J. Zhang, X. X. Ding, H. Lin, H. H. Wen, B. Normand, R. Yu, Weiqiang Yu. 2015-03-28. Nearly-critical spin and charge fluctuations in KFe2As2 observed by high-pressure NMR. https://doi.org/10.1103/physrevb.93.085129

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