Department of Physics, Indian Institute of Science, Bangalore, India.
J Phys Condens Matter. 2010 Jun 30;22(25):255402. doi: 10.1088/0953-8984/22/25/255402. Epub 2010 Jun 7.
We report temperature-dependent Raman spectra of CeFeAsO(0.9)F(0.1) from 4 to 300 K in the spectral range of 60-1800 cm(-1) and interpret them using estimates of phonon frequencies obtained from first-principles density functional calculations. We find evidence for strong coupling between the phonons and crystal field excitations; in particular the Ce(3 + ) crystal field excitation at 432 cm(-1) couples strongly with the E(g) oxygen vibration at 389 cm(-1). Below the superconducting transition temperature, the phonon mode near 280 cm(-1) shows softening, signaling its coupling with the superconducting gap. The ratio of the superconducting gap to T(c), thus estimated to be ~10, suggests CeFeAsO(0.9)F(0.1) to be a strong coupling superconductor. In addition, two high frequency modes observed at 1342 and 1600 cm(-1) are attributed to electronic Raman scattering from the (x(2)-y(2)) to xz /yz d-orbitals of Fe.
我们报告了 CeFeAsO(0.9)F(0.1) 在 4 到 300 K 温度范围内的拉曼光谱，光谱范围为 60-1800 cm(-1)，并使用第一性原理密度泛函计算得到的声子频率估计值对其进行了解释。我们发现声子和晶体场激发之间存在强烈的耦合；特别是 Ce(3+)晶体场激发在 432 cm(-1)处与 389 cm(-1)处的 E(g)氧振动强烈耦合。在超导转变温度以下，约 280 cm(-1)附近的声子模式软化，表明其与超导能隙耦合。由此估计超导能隙与 T(c)的比值约为 10，表明 CeFeAsO(0.9)F(0.1) 是一个强耦合超导体。此外，在 1342 和 1600 cm(-1)处观察到的两个高频模式归因于来自 Fe 的 (x(2)-y(2))到 xz / yz d 轨道的电子拉曼散射。
