Quantum Phases of Kagome Electron System with Half-Filled Flat Bands

Abstract

We study the quantum phase diagram of spinful fermions on kagome lattice with half-filled lowest flat bands. To understand the competition between magnetism, flat band frustration, and repulsive interactions, we adopt an extended $t$-$J$ model, where the hopping energy $t$, antiferromagnetic Heisenberg interaction $J$, and short-range neighboring Hubbard interaction $V$ are considered. In the weak $J$ regime, we identify a fully spin-polarized phase, which can further support the spontaneous Chern insulating phase driven by the short-range repulsive interaction. This phase still emerges with in-plane ferromagnetism, whereas the non-interacting Chern insulator disappears constrained by symmetry. As $J$ gradually increases, the ferromagnetism is suppressed and the system first becomes partially-polarized with large magnetization and then enters a non-polarized phase with the ground state exhibiting vanishing magnetization. We identify this non-polarized phase as an insulator with a nematic charge density wave. In the end, we discuss the potential experimental observations of our theoretical findings.

4 figures, 6 pages, comments are welcome

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Cited by in corpus (7)

• Observation of topological flat bands in the kagome semiconductor Nb${}_3$Cl${}_8$
• Second order Josephson effect in excitonic insulators
• Complex magnetic and spatial symmetry breaking from correlations in kagome flat bands
• Chiral-Flux-Phase-Based Topological Superconductivity in Kagome Systems with Mixed Edge Chiralities
• Unconventional Metallic Magnetism: Non-analyticity and Sign-changing Behavior of Orbital Magnetization in ABC Trilayer Graphene
• Nonreciprocal phonons in PT-symmetric antiferromagnet
• Nature of quantum criticality in the Ising ferromagnet TbV${}_6$Sn${}_6$