Publication details
Magnetic polarons due to spin-length fluctuations in 𝑑4 spin-orbit Mott systems
| Authors | |
|---|---|
| Year of publication | 2025 |
| Type | Article in Periodical |
| Magazine / Source | Physical Review B |
| MU Faculty or unit | |
| Citation | |
| web | |
| Doi | https://doi.org/10.1103/PhysRevB.111.195125 |
| Keywords | Exchange interaction; Polarons; Quantum phase transitions; Spin dynamics; Mott insulators; Diagrammatic methods; Linear spin wave theory |
| Description | Mott insulators based on 4??? and 5??? transition-metal ions, where spin-orbit interaction plays a key role, can exhibit various forms of unusual magnetism. A particular example is the antiferromagnet Ca2?RuO4 containing ??4Ru4+ ions. Here the spin-orbit interaction stabilizes the nonmagnetic ??=0 singlet ionic ground state, which gets dynamically mixed, via exchange interactions, with low-energy ??=1 ionic excitations. Thanks to a sufficient strength of the exchange, these excitations condense and a long-range order emerges. The resulting ordered moments are soft and prone to fluctuations of their effective length. The corresponding amplitude mode appears as a prominent magnetic excitation and complements the conventional magnons involving rotations of the moments. Motivated by this peculiar kind of magnetic order and the specific spectrum of magnetic excitations, we study their influence on the propagation of doped carriers. To this end, we construct a microscopic model including both ??4 and ??5 degrees of freedom and address the propagation of an injected electron by employing self-consistent Born approximation. We find that the electron shows a combination of both free and a polaronic type of motion, where the mobile carrier strongly interacts with an accompanying cloud of magnetic excitations. Remarkably, in the latter case it is the exotic excitation, the amplitude mode, that is found to dominate over the contribution of magnons. Our soft-spin situation thus largely contrasts with spin polarons widely discussed in the context of doped Heisenberg-type magnets based on rigid spin moments. |
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