Abstract
In quantum materials with multiple degrees of freedom such as itinerant electrons and local moments, the interplay between them leads to intriguing phenomena and allows the mutual control of each other. Here, we study band topology and engineering from the interplay between local moments and itinerant electrons in pyrochlore iridates. For metallic , the Ir conduction electrons interact with the Pr local moments via the exchange. While the Ir electrons form a Luttinger semimetal, the Pr moments can be tuned into an ordered spin ice with a finite ordering wave vector, dubbed the Melko-Hertog-Gingras state, by varying Ir and O contents. We point out that the Pr Ising order generates an internal field and reconstructs the Ir bands. Besides the broad existence of Weyl nodes, we predict that the magnetic translation of the Pr Melko-Hertog-Gingras state protects the Dirac-band touching at certain time-reversal invariant momenta for the Ir electrons. We propose the magnetic fields to control the Pr magnetism and thereby indirectly influence the Ir conduction electrons. Our prediction can be immediately tested in ordered samples. Our theory should stimulate experiments on pyrochlore iridates, constitute a nontrivial and realistic example for the interplay between itinerant electrons and local moments in three dimensions, and shed light on hybrid quantum materials with multiple degrees of freedom.
- Received 22 December 2017
- Revised 4 July 2018
DOI:https://doi.org/10.1103/PhysRevX.8.041039
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
Physics Subject Headings (PhySH)
Popular Summary
Topological materials exhibit robust electrical properties that make them potentially useful for a range of new and exotic applications. To better understand these materials, researchers are looking into the interplay between topology and correlation—the former characterizes how electron behavior on the surface corresponds to behavior inside the material, whereas the latter describes electrostatic forces between the electrons. Pyrochlore iridate is one material family that is useful in this regard, as it contains the physics of strong correlation and topology. Here, we develop a theoretical framework for one member of that family, , which reveals the interplay between conduction electrons and local magnetic moments in this system.
Using our framework, we find that the arrangement of spins of the praseodymium (Pr) atoms generates an internal magnetic field that reconstructs the conduction bands of the iridium (Ir) electrons. Application of an external magnetic field should allow one to indirectly control the Ir electrons via the Pr magnetism, thereby driving transitions between various topological phases.
Our work provides a novel perspective for understanding the topological nature in materials induced by the interplay between itinerant electrons and local magnetic moments. We expect our theory, which can be tested with diverse viable experiments, to shed light upon hybrid quantum materials with both local magnetic moments and conduction electrons.
