Kavli Affiliate: Jing Wang
| First 5 Authors: Kejie Bao, Kejie Bao, , ,
| Summary:
We predict the van der Waals monolayer ReAg$_2$Cl$_6$ hosts isolated flat
Chern bands at the Fermi level in its $120^circ$ antiferromagnetic ground
state. Their flatness and nontrivial topology arise from the cooperative effect
of coplanar spin order and strong spin-orbit coupling within Re $5d$ orbitals-a
mechanism distinct from moir’e systems. The spiral spin texture naturally
enlarges the unit cell, reducing carrier densities while preserving sizable
interaction scales. Many-body calculations show that fractional fillings can
support fractional Chern insulator and charge-density wave states. Remarkably,
the mechanism is generic to a broad family of Re-based compounds, with both
spin configuration and flat band topology tunable by electrical manipulation.
Our findings establish Re-based coplanar antiferromagnets as a robust, tunable,
and experimentally accessible platform for flat Chern bands and correlated
topological phases potentially at elevated temperatures.
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