Tunable valley ordering and Fermi surface reconstructions in a moiré magnet.

Interlayer interactions in van der Waals materials are pivotal in stabilizing electronic phases. Notably, the 'magic' rotation of two graphene layers has recently emerged as a versatile platform for manipulating interlayer hybridization. This significantly modifies the band structure, resulting in a superlattice with extremely flat bands at low energies. Such flat bands, characterized by a high density of states and strong Coulomb repulsion, give rise to
diverse correlated phases in magic-angle twisted bilayer graphene (MATBG), ranging from insulating to superconducting and magnetic states. Despite its unprecedented tunability, a complete understanding of the observed phases in MATBG remains elusive. In this talk, I will
provide a brief overview of various twisted graphene-based moiré superlattices developed in the years following the discovery of MATBG. Subsequently, I will present our recent findings from magneto-transport measurements on MATBG proximitized by a tungsten diselenide layer, introducing finite spin-orbit coupling. Our primary results reveal an anomalous Hall effect near half-filling (ν = 2), coupled with an abrupt switching of magnetization tunable by carrier density. Near ν = 2, we observe Fermi surface reconstructions in the zero-magnetic field limit, evolving into a quantized Chern insulator precisely at ν = 2 with increasing magnetic field. These intriguing results collectively suggest that the bands are valley-polarized and malleable near ν = 2, stabilized by spin-orbit coupling. In the end, I will briefly mention our ongoing work, exploring the malleability of the bands through time-reversal symmetric nonlinear transport measurements.