Manifestation of nematic degrees of freedom in the Raman response function of iron pnictides
Manifestation of nematic degrees of freedom in the Raman response function of iron pnictides
复制标题
铁磷族化合物拉曼响应函数中向列自由度的表现
DOI：
10.1103/physrevb.92.075134
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发表时间：
2015
影响因子：
3.7
通讯作者：
J. Schmalian
中科院分区：
文献类型：
--
作者：
U. Karahasanović;F. Kretzschmar;T. Böhm;R. Hackl;I. Paul;Y. Gallais;J. Schmalian
在铁基超导体电子向列性的自旋驱动方法中，我们建立了通道中的拉曼响应函数与电子对向列磁化率的贡献之间的关系。自旋驱动的向列相是由条纹相相关的磁波动产生的，其特征是对称性断裂，但自旋旋转对称性没有断裂。在结构相变和磁相变分离的体系中，它作为一个单独的相出现。探测铁基超导体中向列自由度的存在是一项艰巨的任务，因为它涉及测量高阶自旋相关函数。我们证明了向列自由度在实验可测量的拉曼响应函数中表现出来。考虑高阶Aslamazov-Larkin型图，计算了大极限下四方相的拉曼响应函数。它们的特点是由电子激发介导的一系列插入的四次顺磁偶联，类似于理论的向列耦合常数。这些图有效地解释了自旋涨落之间的碰撞。通过对无数个这样的高阶图求和，我们证明了电子拉曼响应函数在通道的结构相变处有一个明显的最大值。因此，拉曼响应函数可以用来探测向列自由度。
We establish a relation between the Raman response function in thechannel and the electronic contribution to the nematic susceptibility within the spin-driven approach to electron nematicity of the iron-based superconductors. The spin-driven nematic phase, characterized by the brokensymmetry, but unbrokenspin-rotational symmetry, is generated by the presence of magnetic fluctuations associated with the striped phase. It occurs as a separate phase betweenandin systems where the structural and magnetic phase transitions are separated. Detecting the presence of nematic degrees of freedom in iron-based superconductors is a difficult task, since it involves measuring higher-order spin-correlation functions. We show that the nematic degrees of freedom manifest themselves in the experimentally measurable Raman response function. We calculate the Raman response function in the tetragonal phase in the large-limit by considering higher-order Aslamazov–Larkin type of diagrams. They are characterized by a series of inserted quartic paramagnon couplings mediated by electronic excitations that resemble the nematic coupling constant of the theory. These diagrams effectively account for collisions between spin fluctuations. By summing an infinite number of such higher-order diagrams, we demonstrate that the electronic Raman response function shows a clear maximum at the structural phase transition in thechannel. Hence, the Raman response function can be used to probe nematic degrees of freedom.