Interdependence of the relaxation of spin and charge degrees of freedom in ferromagnetic AxByMnO3 compounds during the first ten picoseconds after optical excitation

光激发后前十皮秒期间铁磁 AxByMnO3 化合物中自旋和电荷自由度弛豫的相互依赖性

• 批准号: 5372866
• 负责人: Professor Dr. Hartmut G. Roskos
• 金额: --
• 依托单位: Physikalisches Institut
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2002
• 资助国家: 德国
• 起止时间: 2001-12-31 至 2004-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5372866?language=en
• 关键词: Interdependence; relaxation; spin; charge; degrees

Three topics will be addressed: Energy relaxation: Pump/probe measurements pertaining to the energy relaxation of the charge carriers in La0.67Ca0.33Mn03 have shown a remarkable decrease of the relaxation rate when the sample temperature is reduced. This observation is tentatively explained with less effective scattering of charge carriers across an energy gap which increases with the magnetization of the sample. Estimates suggest that the k-dependence of the Froehlich interaction of electrons and phonons together with a widening energy gap may account for the observed temperature dependence. This will be tested with more detailed model calculations. Spin relaxation: If the carrier relaxation is dominated by a magnetization gap between spin-split bands, the relaxation across the gap should involve a spin flip. In this case, the early spin relaxation process should slow down concomitant with the energy relaxation when the temperature is decreased. Coherent phonons: Our experimental data exhibit signatures of strongly damped low-frequency coherent phonons. Measurements with improved signal-to noise ration are planned to test the hypothesis that the coherent phonons are associated with Jahn-Teller distortions of the lattice. If this can be verified, more systematic studies promise insight into the interplay of carrier/spin relaxation and lattice dynamics.

将讨论三个主题： 能量弛豫：与 La0.67Ca0.33Mn03 中载流子能量弛豫相关的泵浦/探针测量表明，当样品温度降低时，弛豫率显着降低。这一观察结果暂时被解释为电荷载流子在能隙上的散射效果较差，能隙随样品的磁化强度而增加。估计表明，电子和声子的 Froehlich 相互作用的 k 依赖性以及加宽的能隙可能解释了观察到的温度依赖性。这将通过更详细的模型计算进行测试。自旋弛豫：如果载流子弛豫由自旋分裂带之间的磁化间隙主导，则跨间隙的弛豫应涉及自旋翻转。在这种情况下，当温度降低时，早期自旋弛豫过程应随着能量弛豫而减慢。相干声子：我们的实验数据表现出强阻尼低频相干声子的特征。计划采用改进的信噪比进行测量，以检验相干声子与晶格的 Jahn-Teller 畸变相关的假设。如果这一点能够得到证实，更系统的研究有望深入了解载流子/自旋弛豫和晶格动力学的相互作用。