Orbital-driven nematicity in FeSe
Orbital-driven nematicity in FeSe
复制标题
DOI：
10.1038/nmat4138
复制
发表时间：
2015-02-01
期刊：
影响因子：
41.2
通讯作者：
Buechner, B.
中科院分区：
文献类型：
--
作者：
Baek, S-H.;Efremov, D. V.;Buechner, B.
铁基材料中超导性的一个基本和非常规特征是它发生在另外两个不稳定性附近。除了倾向于磁秩序，这些铁基系统有一个倾向的磁有序：一个降低的旋转对称性，而保留时间反演不变性。为超导性奠定了基础，人们激烈地争论着对称性破缺是否是由晶格、轨道或自旋自由度驱动的。在这里，我们报告了一个非常清楚的分裂的NMR共振线在FeSe在T-nem = 91 K，远高于超导Tc的9.3 K。分裂发生在垂直于Fe平面的磁场中，并且具有朗道型序参量的温度依赖性。自旋-晶格弛豫速率在T-nem处不受影响，这明确地建立了轨道自由度作为驱动的π阶。我们证明了超导性与新兴的向列性竞争。
A fundamental and unconventional characteristic of superconductivity in iron-based materials is that it occurs in the vicinity of two other instabilities. In addition to a tendency towards magnetic order, these Fe-based systems have a propensity for nematic ordering: a lowering of the rotational symmetry while time-reversal invariance is preserved. Setting the stage for superconductivity, it is heavily debated whether the nematic symmetry breaking is driven by lattice, orbital or spin degrees of freedom. Here, we report a very clear splitting of NMR resonance lines in FeSe at T-nem = 91 K, far above the superconducting T-c of 9.3 K. The splitting occurs for magnetic fields perpendicular to the Fe planes and has the temperature dependence of a Landau-type order parameter. Spin-lattice relaxation rates are not affected at T-nem, which unequivocally establishes orbital degrees of freedom as driving the nematic order. We demonstrate that superconductivity competes with the emerging nematicity.