Crystal-field excitations and quadrupolar fluctuations of 4f-electron systems studied by polarized light scattering
Crystal-field excitations and quadrupolar fluctuations of 4f-electron systems studied by polarized light scattering
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DOI：
10.1088/1742-6596/2164/1/012054
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
M. Ye;H. Kung;P. Rosa;E. Rosenberg;J. Kim;X. H. Xu;E. Bauer;Z. Fisk;I. Fisher;S. Cheong;G. Blumberg
中科院分区：
文献类型：
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作者：
M. Ye;H. Kung;P. Rosa;E. Rosenberg;J. Kim;X. H. Xu;E. Bauer;Z. Fisk;I. Fisher;S. Cheong;G. Blumberg
我们展示了 CeB6、TbInO3 和 YbRu2Ge2 三种材料的拉曼散射结果，以说明晶体场 (CF) 激发和 4f 电子系统四极波动的基本方面。对于 CF 激发，我们通过展示大能量范围内的多重线间和内部多重激发的光谱来说明 4f 轨道如何被自旋轨道耦合和 CF 势分裂。我们从测量的 CF 激发的对称性和能量讨论了 CF 基态的识别和低能 CF 能级方案的建立。此外，我们还证明CF线宽是利用自能效应来检测电子相关性的敏感探针。对于四极波动，我们讨论铁四极（FQ）和反铁四极（AFQ）情况。与 FQ 序参数具有相同对称性的长波长四极涨落持续远高于转变温度，由此可以评估电子位点间四极相互作用的强度。 AFQ 排序的趋势会引起相邻 4f 离子位点之间的铁磁相关性，从而导致长波长磁波动。
We present Raman-scattering results for three materials, CeB6, TbInO3, and YbRu2Ge2, to illustrate the essential aspects of crystal-field (CF) excitations and quadrupolar fluctuations of 4f-electron systems. For CF excitations, we illustrate how the 4f orbits are split by spin-orbit coupling and CF potential by presenting spectra for inter- and intra-multiplet excitations over a large energy range. We discuss identification of the CF ground state and establishment of low-energy CF level scheme from the symmetry and energy of measured CF excitations. In addition, we demonstrate that the CF linewidth is a sensitive probe of electron correlation by virtue of self-energy effect. For quadrupolar fluctuations, we discuss both ferroquadrupolar (FQ) and antiferroquadrupolar (AFQ) cases. Long-wavelength quadrupolar fluctuations of the same symmetry as the FQ order parameter persists well above the transition temperature, from which the strength of electronic intersite quadrupolar interaction can be evaluated. The tendency towards AFQ ordering induces ferromagnetic correlation between neighboring 4f-ion sites, leading to long-wavelength magnetic fluctuations.