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Antiferromagnetic insulators present a promising alternative to ferromagnets due to their ultrafast spin dynamics essential for low-energy terahertz spintronic device applications. Magnons, i.e., quantized spin waves capable of transmitting information through excitations, serve as a key functional element in this paradigm. However, identifying external mechanisms to effectively tune magnon properties has remained a major challenge. Here we demonstrate that interfacial metal-insulator transitions offer an effective method for controlling the magnons of Sr2IrO4, a strongly spin-orbit coupled antiferromagnetic Mott insulator. Resonant inelastic x-ray scattering experiments reveal a significant softening of zone-boundary magnon energies in Sr2IrO4 films epitaxially interfaced with metallic 4d transition-metal oxides. Therefore, the magnon dispersion of Sr2IrO4 can be tuned by metal-insulator transitions of the 4d transition-metal oxides. We tentatively attribute this non-trivial behavior to a long-range phenomenon mediated by magnon-acoustic phonon interactions. Our experimental findings introduce a strategy for controlling magnons and underscore the need for further theoretical studies to better understand the underlying microscopic interactions between magnons and phonons.
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This content will become publicly available on October 1, 2026
Magnon-polarons in the Fermi–Hubbard model
The interplay of magnetic excitations and itinerant charge carriers is a ubiquitous phenomenon in strongly correlated electron systems. A key theoretical question is understanding the renormalization of the magnon quasiparticle, a collective spin excitation, upon doping a magnetic insulator. Here we observe a new type of quasiparticle—a magnon-Fermi-polaron—arising from the dressing of a magnon with the doped holes of a cold-atom Fermi–Hubbard system. Using Raman excitation with controlled momentum in a doped, spin-polarized band insulator, we address the spectroscopic properties of the magnon-polaron. In an undoped system with strong interactions, photoexcitation produces magnons, whose properties are accurately described by spin-wave theory. We measure the evolution of the photoexcitation spectra as we move away from this limit to produce magnon-polarons due to dressing of the magnons by charge excitations. We observe a shift in the polaron energy with doping that is strongly dependent on the injected momentum, accompanied by a reduction of spectral weight in the probed energy window. We anticipate that the technique introduced here, which is the analogue of inelastic neutron scattering, will provide atomic quantum simulators with access to the dynamics of a wide variety of excitations in strongly correlated phases.
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- Award ID(s):
- 2110475
- PAR ID:
- 10650158
- Publisher / Repository:
- Nature Publishing Group UK London
- Date Published:
- Journal Name:
- Nature Physics
- Volume:
- 21
- Issue:
- 10
- ISSN:
- 1745-2473
- Page Range / eLocation ID:
- 1548 to 1554
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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