Phonon anomalies in pyrochlore iridates studied by Raman spectroscopy
Phonon anomalies in pyrochlore iridates studied by Raman spectroscopy
复制标题
用拉曼光谱研究烧绿石虹彩中的声子异常
作者：
K. Ueda;R. Kaneko;A. Subedi;M. Minola;B. J. Kim;J. Fujioka;Y. Tokura;B. Keimer
我们报告的偏振分辨拉曼散射测量单晶烧绿石化合物Eu 2 Ir 2 O 7表现出基态与非共线磁序，以及其顺磁对应物Pr 2 Ir 2 O 7。光谱揭示了六拉曼活性光学声子预期的烧绿石晶格对称性。结合密度泛函计算，偏振分析的拉曼强度使我们能够指定所有观察到的峰的speci（cid：12）c振动模式。Eu 2 Ir 2 O 7中的Ir-O-Ir键弯曲振动在顺磁状态下表现出明显的Fano不对称性，在磁相变时表现出明显的软化和线形异常。这些观测结果表明强烈的电子-声子相互作用，这必须考虑在模型的电子性质和相行为的烧绿石铱酸盐。此外，Eu 2 Ir 2 O 7的拉曼光谱在低于磁转变温度时出现了显著的磁振子模。
We report polarization-resolved Raman scattering measurements on single crystals of the pyrochlore compound Eu 2 Ir 2 O 7 which exhibits a ground state with non-collinear magnetic order, as well as its paramagnetic counterpart Pr 2 Ir 2 O 7 . The spectra reveal the six Raman-active optical phonons expected for the pyrochlore lattice symmetry. Combined with density functional calculations, polarization analysis of the Raman intensity allows us to assign all observed peaks to speci(cid:12)c vibration patterns. Whereas most phonon pro(cid:12)les are weakly temperature dependent, an Ir-O-Ir bond-bending vibration in Eu 2 Ir 2 O 7 exhibits a pronounced Fano asymmetry in the paramagnetic state, and marked softening and lineshape anomalies at the magnetic phase transition. These observations indicate strong electron-phonon interactions, which must be considered in models of the electronic properties and phase behavior of the pyrochlore iridates. In addition, a prominent magnon mode appears in the Raman spectrum of Eu 2 Ir 2 O 7 below the magnetic transition temperature.