Interaction-driven spontaneous ferromagnetic insulating states with odd Chern numbers

• Published in: npj quantum materials Vol. 8; no. 1; pp. 14 - 7
• Main Authors: Mai, Peizhi, Huang, Edwin W., Yu, Jiachen, Feldman, Benjamin E., Phillips, Philip W.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09.03.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/2793; 639/766/119/2794; Antiferromagnetism; Compressibility; Condensed Matter Physics; Electromagnetism; Energy; Ferromagnetism; Graphene; Laboratories; Magnetic fields; MATERIALS SCIENCE; Monte Carlo simulation; Physics; Physics and Astronomy; Quantum Physics; Structural Materials; Surfaces and Interfaces; Symmetry; Thin Films
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-023-00544-z

Motivated by recent experimental work on moiré systems in a strong magnetic field, we compute the compressibility as well as the spin correlations and Hofstadter spectrum of spinful electrons on a honeycomb lattice with Hubbard interactions using the determinantal quantum Monte Carlo method. While the interactions in general preserve quantum and anomalous Hall states, emergent features arise corresponding to an antiferromagnetic insulator at half-filling and other incompressible states following the Chern sequence ± (2 N  + 1). These odd integer Chern states exhibit strong ferromagnetic correlations and arise spontaneously without any external mechanism for breaking the spin-rotation symmetry. Analogs of these magnetic states should be observable in general interacting quantum Hall systems. In addition, the interacting Hofstadter spectrum is qualitatively similar to the experimental data at intermediate values of the on-site interaction.