Realization of the Haldane Chern insulator in a moiré lattice

Kavli Affiliate: Jie Shan

| First 5 Authors: Wenjin Zhao, Kaifei Kang, Lizhong Li, Charles Tschirhart, Evgeny Redekop

| Summary:

The Chern insulator displays a quantized Hall effect without Landau levels.
In a landmark paper in 1988, Haldane showed that a Chern insulator could be
realized through complex next-nearest-neighbor hopping in a honeycomb lattice.
Despite its profound impact on the field of topological physics and recent
implementation in cold-atom experiments, the Haldane model has remained elusive
in solid-state materials. Here, we report the experimental realization of a
Haldane Chern insulator in AB-stacked MoTe2/WSe2 moir’e bilayers, which form a
honeycomb moir’e lattice with two sublattices residing in different layers. We
show that the moir’e bilayer filled with two charge particles per unit cell is
a quantum spin Hall (QSH) insulator with a tunable charge gap. Under a small
out-of-plane magnetic field, it becomes a Chern insulator with Chern number c=1
from magneto-transport studies. The results are qualitatively captured by a
generalized Kane-Mele tight-binding Hamiltonian. The Zeeman field splits the
QSH insulator into two halves of opposite valley–one with a positive and the
other a negative moir’e band gap. Our study highlights the unique potential of
semiconductor moir’e materials in engineering topological lattice

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