Abstract
We point out the emergence of magnetism from the interplay of electron quasi-itinerancy and quantum order by disorder in pyrochlore iridates. Like other Mott insulating iridates, the ion in pyrochlore iridates develops an effective moment from the on-site spin-orbit coupling. We consider the generic symmetry-allowed exchange between these local moments on a pyrochlore lattice and obtain the mean-field phase diagram. Assuming the superexchange is mediated by direct and/or indirect electron hopping via intermediate oxygens, we derive the exchange interactions in the strong-coupling regime from the Hubbard model. This exchange has a degenerate classical ground-state manifold, and quantum fluctuation selects a noncoplanar ground state, known as quantum order by disorder. Extending to the intermediate-coupling regime, the same noncoplanar order is selected from the degenerate manifold by the kinetic energy, which is dubbed “electron quasi-itinerancy.” We discuss the experimental relevance of our results and electron quasi-itinerancy among other iridates and magnets.
1 More- Received 6 August 2020
- Accepted 4 November 2020
DOI:https://doi.org/10.1103/PhysRevResearch.2.043273
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society