To elucidate the magnetic structure and the origin of the nematicity in FeSe, we perform a high-pressure 77Se NMR study on FeSe single crystals. We find a suppression of the structural transition temperature with pressure up to about 2 GPa from the anisotropy of the Knight shift. Above 2 GPa, a stripe-order antiferromagnetism that breaks the spatial four-fold rotational symmetry is determined by the NMR spectra under different field orientations and with temperatures down to 50 mK. The magnetic phase transition is revealed to be first-order type, implying the existence of a concomitant structural transition via a spin-lattice coupling. Stripe-type spin fluctuations are observed at high temperatures, and remain strong with pressure. These results provide clear evidences for strong coupling between nematicity and magnetism in FeSe, and therefore support a universal scenario of magnetic driven nematicity in iron-based superconductors.
@article{arxiv.1603.04589,
title = {Pressure Induced Stripe-order Antiferromagnetism and First-order Phase Transition in FeSe},
author = {P. S. Wang and S. S. Sun and Y. Cui and W. H. Song and T. R. Li and Rong Yu and Hechang Lei and Weiqiang Yu},
journal= {arXiv preprint arXiv:1603.04589},
year = {2016}
}
Comments
6 pages, 4 figures. This paper has been accepted by Physical Review Letters