Kavli Affiliate: Jie Shan
| First 5 Authors: Patrick Knüppel, Jiacheng Zhu, Yiyu Xia, Zhengchao Xia, Zhongdong Han
| Summary:
Twisted bilayers of transition metal dichalcogenide (TMD) semiconductors have
emerged as a highly tunable system for the studies of correlated and
topological states of matter, such as superconductivity, ferromagnetism,
correlated insulators, and topological and Chern insulators. However, the
connection between these symmetry-breaking ground states and the underlying
band structure singularity in these materials remains largely unexplored. Here,
by combining exciton sensing and magnetic circular dichroism (MCD)
measurements, we demonstrate how the magnetic properties and the correlated
insulating states are controlled by the gate tunable van Hove singularity (VHS)
in the band structure of twisted bilayer WSe2 (tWSe2). In particular, we
demonstrate how the location of the VHS in the tWSe2 band structure can
influence 1) the stability of Stoner ferromagnetism, 2) the valley
polarizability and the stability of Chern insulators, as well as 3) the layer
polarizability and the associated metal-insulator transition. The results are
supported by continuum model band structure calculations. Our work highlights
an important ingredient for understanding the electronic phase diagram in
twisted bilayer TMDs.
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