论文标题
通过电子和离子拉曼散射在laalo $ _3 $中产生相干声子的比较
Comparison of coherent phonon generation by electronic and ionic Raman scattering in LaAlO$_3$
论文作者
论文摘要
在离子拉曼散射中，红外活性声子介导了散射过程，从而导致或破坏拉曼活跃的声子。这种机制依赖于声子之间的非线性相互作用，并且近年来与复杂的过渡金属氧化物中的各种新兴晶格驱动的现象有关，但是基本机制通常由于存在多个耦合顺序的顺序参数而掩盖了基本机制。在这里，我们使用时间分辨光谱法比较了由离子拉曼散射产生的相干声子与在非磁性和非磁性宽带宽带绝缘子Laalo $ _3 $中产生的相干散射产生的相干声子。我们发现低频拉曼活性$ e_g $模式的振荡幅度在我们将泵频率调整为与高频红外活性$ e_U $模式时相连的峰值峰值，与第一原则计算一致。我们的结果表明，离子拉曼散射可以在宽带隙绝缘材料中强烈主导电子拉曼散射。我们还看到了在28〜mj/cm $^2 $高于28〜mj/cm $^2 $的散射通道的证据，这些通道改变了相干声子响应的测得幅度。
In ionic Raman scattering, infrared-active phonons mediate a scattering process that results in the creation or destruction of a Raman-active phonon. This mechanism relies on nonlinear interactions between phonons and has in recent years been associated with a variety of emergent lattice-driven phenomena in complex transition-metal oxides, but the underlying mechanism is often obscured by the presence of multiple coupled order parameters in play. Here, we use time-resolved spectroscopy to compare coherent phonons generated by ionic Raman scattering with those created by more conventional electronic Raman scattering on the nonmagnetic and non-strongly-correlated wide band-gap insulator LaAlO$_3$. We find that the oscillatory amplitude of the low-frequency Raman-active $E_g$ mode exhibits a sharp peak when we tune our pump frequency into resonance with the high-frequency infrared-active $E_u$ mode, consistent with first-principles calculations. Our results suggest that ionic Raman scattering can strongly dominate electronic Raman scattering in wide band-gap insulating materials. We also see evidence of competing scattering channels at fluences above 28~mJ/cm$^2$ that alter the measured amplitude of the coherent phonon response.
