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arXiv · 1805.03493

Dynamic spin-lattice coupling and nematic fluctuations in NaFeAs

Yu Li·1 Zahra Yamani·2 Yu Song·1 Weiyi Wang·1 Chenglin Zhang·1 David W. Tam·Tong Chen·Ding Hu·Zhuang Xu·Songxue Chi·Ke Xia·Li Zhang·Shifeng Cui·Wenan Guo·Ziming Fang·Yi Liu·Pengcheng Dai
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Abstract

We use inelastic neutron scattering to study acoustic phonons and spin excitations in single crystals of NaFeAs, a parent compound of iron pnictide superconductors. NaFeAs exhibits a tetragonal-to-orthorhombic structural transition at $T_s\approx 58$ K and a collinear antiferromagnetic (AF) order at $T_N\approx 45$ K. While longitudinal and out-of-plane transverse acoustic phonons behave as expected, the in-plane transverse acoustic phonons reveal considerable softening on cooling to $T_s$, and then harden on approaching $T_N$ before saturating below $T_N$. In addition, we find that spin-spin correlation lengths of low-energy magnetic excitations within the FeAs layer and along the $c$-axis increase dramatically below $T_s$, and show weak anomaly across $T_N$. These results suggest that the electronic nematic phase present in the paramagnetic tetragonal phase is closely associated with dynamic spin-lattice coupling, possibly arising from the one-phonon-two-magnon mechanism.

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Yu Li, 1 Zahra Yamani, 2 Yu Song, 1 Weiyi Wang, 1 Chenglin Zhang, 1 David W. Tam, Tong Chen, Ding Hu, Zhuang Xu, Songxue Chi, Ke Xia, Li Zhang, Shifeng Cui, Wenan Guo, Ziming Fang, Yi Liu, Pengcheng Dai. 2018-05-09. Dynamic spin-lattice coupling and nematic fluctuations in NaFeAs. https://doi.org/10.1103/physrevx.8.021056

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