Isolated nearly flat higher Chern band in monolayer transition metal trihalides

Kavli Affiliate: Jing Wang

| First 5 Authors: Kejie Bao, Huan Wang, Yadong Jiang, Haosheng Xu, Jing Wang

| Summary:

The interplay between non-trivial topology and strong electron interaction
can generate a variety of exotic quantum matter. Here we theoretically propose
that monolayer transition metal trihalides MoF$_3$ and WI$_3$ have isolated
nearly flat band near the Fermi level with higher Chern number $mathcal{C}=+3$
and $mathcal{C}=-2$, respectively. The nontrivial topology of these flat Chern
bands originates from the effective $sd^2$ hybridization of transition metal
atom, which transform the apparent atomic $d$ orbitals on a hexagonal lattice
into $(s, p_+, p_-)$ orbitals on a triangular lattice. Interestingly, the
quantum geometry of flat Chern bands in both materials are comparable with
those in moir’e systems exhibiting fractional Chern insulator state. The
Hofstadter butterfly of such flat Chern bands are further studied. These
natural materials, if realized experimentally, could offer new platforms to
explore correlated phenomena driven by flat Chern band with higher Chern
number.

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