Abstract
Novel phenomena in magnetically intercalated graphite have been the subject of much research, pioneered and promoted by M. S. and G. Dresselhaus and many others in the 1980s. Among the most enigmatic findings of that era was the dramatic, roller-coaster-like behavior of the magnetoresistivity in a compound, in which magnetic ions form a triangular lattice that is commensurate to graphite honeycomb planes. In this study, we provide a long-awaited microscopic explanation of this behavior, demonstrating that the resistivity of is dominated by spin excitations in Eu planes and their highly nontrivial evolution with the magnetic field. Together with our theoretical analysis, the present study showcases the power of the synthetic 2D materials as a source of potentially significant insights into the nature of exotic spin excitations.
- Received 21 September 2021
- Revised 12 November 2021
- Accepted 15 February 2022
DOI:https://doi.org/10.1103/PhysRevX.12.021010
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
The diverse physical properties of 2D atomically thin graphene and its multilayered cousins are the subject of intense and highly publicized experimental and theoretical investigations that define modern condensed-matter physics and materials science. They realize previously unexplored physical regimes in electron transport, superconductivity, magnetism, and topological phenomena and also hold a significant promise for future technology. Our theoretical study focuses on a lesser-known predecessor—the graphite compound —and explains highly unusual behavior in its resistivity.
In , magnetic atoms of europium (Eu) insert themselves between 2D layers of graphite, forming a “magnetically intercalated” material, in which conduction electrons in graphite layers and magnetic moments (or spins) of Eu are strongly coupled. The Eu atoms form triangular lattice layers in which their spins realize one of the iconic models of frustrated magnetism—the triangular lattice antiferromagnet, the spin configuration of which follows a specific sequence of patterns under the applied magnetic field.
The resistivity of this material has a unique “roller-coaster” behavior, wherein the resistance varies in a highly nonmonotonic, oscillatory way as the magnetic field increases from zero to about 20 T. We show that this roller-coaster behavior is caused by the scattering of electrons on magnons, the elementary spin excitations of triangular Eu planes. Namely, magnetic-field-induced changes in the spin configuration result in dramatic changes in the electron-magnon scattering rate that determines the electrical resistivity of the material.
Our investigation yields predictions of new field- and doping-induced phenomena in magnetically intercalated graphite and related systems. It lays out the theoretical framework for treating electron-magnon interaction in frustrated quantum magnets and points out several promising research directions that appear to be within the reach of modern experimental capabilities.
