Comparison of coherent phonon generation by electronic and ionic Raman scattering in LaAlO${}_3$

Abstract

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.

arXiv comment10 pages, 6 figures

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Cited by in corpus (5)

• The Persistence of Memory in Ionic Conduction Probed by Nonlinear Optics
• Ultrafast simultaneous manipulation of multiple ferroic orders through nonlinear phonon excitation
• Light-induced translation symmetry breaking via nonlinear phononics
• A Strategy to Identify Materials Exhibiting a Large Nonlinear Phononics Response: Tuning the Ultrafast Structural Response of LaAlO${}_3$ with Pressure
• Terahertz-driven parametric excitation of Raman-active phonons in LaAlO${}_3$