Integer and fractional moiré Chern insulators in van der Waals bilayers

Moiré van der Waals (vdW) materials have become established playground for exploring band topology and strong-correlations phenomena. Cryogenic nanopositioning and nanorotating setups of attocube systems are widely used in such nanoscale studies because they provide supreme stability and ultra-low-vibrations environment. These cryogenic scanning setups include confocal microscopes and various scanning probe microscopes, ranging from magnetic force microscope (MFM), SQUID microscope and nitrogen vacancy (NV) microscope to single-electron-transistor (SET) microscope and microwave impedance microscope (MIM).

We present here a selection of remarkable results achieved with attocube systems technology in labs of our customers with emphasis on integer and fractional moiré Chern insulators (MCIs) in vdW bilayers: Scanning magnetometry of an integer MCI MoTe₂/WSe₂ shows that its magnetization can be flipped with a very low current [1], which is appealing for utilization in energy-efficient magnetic memories. Magneto-optical study of the same heterostructure discovered a valley-nonpolarized quantum anomalous Hall state [2]. Magic angle twisted bilayer graphene (MATBG), identified as an integer MCI [3], reveals orbital magnetism induced by local Berry curvature as the function of the integer filling factor [4]. Moreover, MATBG can also exhibit fractional Chern insulating states (FCIS) even in low magnetic fields B<12T [5]. FCIS that survive in B=0 have been identified magneto-optically in twisted bilayer MoTe₂ using trions as the local probe for real-space imaging of spin polarization [6].

[1] C. L. Tschirhart et al., Nature Physics 19, 807 (2023).

[2] Z. Tao et al., preprint at https://arxiv.org/abs/2208.07452 (2022).

[3] J. Yu et al., Nature Physics 18, 825 (2022).

[4] S. Grover et al., Nature Physics 18, 885 (2022).

[5] Y. Xie et al., Nature 600, 439 (2021).

[6] J. Cai et al., Nature 622, 63 (2023)