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arXiv · 1802.09980

Nematicity and magnetism in LaFeAsO single crystals probed by $^{75}$As nuclear magnetic resonance

J. M. Ok·S. -H. Baek·D. V. Efremov·R. Kappenberger·S. Aswartham·J. S. Kim·J. van den Brink·B. Büchner
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Abstract

We report a $^{75}$As nuclear magnetic resonance study in LaFeAsO single crystals, which undergoes nematic and antiferromagnetic transitions at $T_\text{nem}\sim 156$ K and $T_N \sim 138$ K, respectively. Below $T_\text{nem}$, the $^{75}$As spectrum splits sharply into two for an external magnetic field parallel to the orthorhombic $a$ or $b$ axis in the FeAs planes. Our analysis of the data demonstrates that the NMR line splitting arises from an electronically driven rotational symmetry breaking. The $^{75}$As spin-lattice relaxation rate as a function of temperature shows that spin fluctuations are strongly enhanced just below $T_\text{nem}$. These NMR findings indicate that nematic order promotes spin fluctuations in magnetically ordered LaFeAsO, as observed in non-magnetic and superconducting FeSe. We conclude that the origin of nematicity is identical in both FeSe and LaFeAsO regardless of whether or not a long range magnetic order develops in the nematic state.

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J. M. Ok, S. -H. Baek, D. V. Efremov, R. Kappenberger, S. Aswartham, J. S. Kim, J. van den Brink, B. Büchner. 2018-05-23. Nematicity and magnetism in LaFeAsO single crystals probed by $^{75}$As nuclear magnetic resonance. https://doi.org/10.1103/physrevb.97.180405

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