Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada.
Phys Rev Lett. 2012 Dec 14;109(24):247001. doi: 10.1103/PhysRevLett.109.247001. Epub 2012 Dec 10.
We report a (75)As single crystal NMR investigation of LaFeAsO, the parent phase of a pnictide high T(c) superconductor. We demonstrate that spin dynamics develop a strong twofold anisotropy within each orthorhombic domain below the tetragonal-orthorhombic structural phase transition at T(TO) ≈ 156 K. This intermediate state with a dynamical breaking of the rotational symmetry freezes progressively into a spin density wave below T(SDW) ≈ 142 K. Our findings are consistent with the presence of a spin nematic state below T(TO) with an incipient magnetic order.
我们报告了 LaFeAsO（一种高温超导的磷化物母体相）的 (^{75}As) 单晶 NMR 研究。我们证明，在四方-正交结构相变温度 T(TO) ≈ 156 K 以下，每个正交畴内的自旋动力学发展出强烈的两倍各向异性。这个具有旋转对称性动力学破坏的中间状态在下一个自旋密度波相变温度 T(SDW) ≈ 142 K 以下逐渐冻结。我们的发现与在 T(TO)以下存在具有初始磁序的自旋向列态一致。
