4d and 5d Transition-Metal Oxide Heterostructures: A New Venue for Tunable Terahertz Magnons
ORAL · Invited
Abstract
Heterostructures of 4d and 5d transition-metal oxides offer an exciting platform for exploring tunable spin dynamics and magnonic phenomena. Among these, antiferromagnetic insulators with strong spin-orbit coupling, such as Sr₂IrO₄, present unique opportunities for terahertz magnonics due to their ultrafast spin dynamics and sensitivity to interfacial effects. However, achieving precise control of magnon propagation through external stimuli remains challenging.
In this talk, we discuss Sr₂IrO₄, a quasi-two-dimensional antiferromagnetic insulator with Jeff = 1/2 pseudospins, whose terahertz spin waves respond strongly to interfacial modifications. Using resonant inelastic x-ray scattering (RIXS), we systematically probed the spin-wave dispersion of Sr₂IrO₄ thin films interfaced with metallic and insulating substrates. Our results reveal a notable softening of single-magnon modes near the (π/2, π/2) zone boundary in films adjacent to metallic substrates, while the magnon spectrum remains unchanged for insulating interfaces. Complementary Raman spectroscopy highlights two-magnon excitations and a significant hardening of phonon modes near metallic interfaces, pointing to electron-phonon interactions as the primary mechanism.
These findings suggest that interfacial electron-phonon coupling modifies phonons in Sr₂IrO₄, which, in turn, influence magnons via long-range magnon-phonon interactions. This mechanism provides a novel means to control terahertz magnon propagation, distinct from conventional interfacial effects such as strain or doping. By leveraging metal-insulator transitions and interfacial phenomena, this work highlights the potential of 4d and 5d transition-metal oxide heterostructures for advancing our understanding of magnonics.
In this talk, we discuss Sr₂IrO₄, a quasi-two-dimensional antiferromagnetic insulator with Jeff = 1/2 pseudospins, whose terahertz spin waves respond strongly to interfacial modifications. Using resonant inelastic x-ray scattering (RIXS), we systematically probed the spin-wave dispersion of Sr₂IrO₄ thin films interfaced with metallic and insulating substrates. Our results reveal a notable softening of single-magnon modes near the (π/2, π/2) zone boundary in films adjacent to metallic substrates, while the magnon spectrum remains unchanged for insulating interfaces. Complementary Raman spectroscopy highlights two-magnon excitations and a significant hardening of phonon modes near metallic interfaces, pointing to electron-phonon interactions as the primary mechanism.
These findings suggest that interfacial electron-phonon coupling modifies phonons in Sr₂IrO₄, which, in turn, influence magnons via long-range magnon-phonon interactions. This mechanism provides a novel means to control terahertz magnon propagation, distinct from conventional interfacial effects such as strain or doping. By leveraging metal-insulator transitions and interfacial phenomena, this work highlights the potential of 4d and 5d transition-metal oxide heterostructures for advancing our understanding of magnonics.
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Presenters
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Ambrose Seo
University of Kentucky
Authors
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Ambrose Seo
University of Kentucky