Abstract

Moiré semiconductors offer flat bands where Coulomb interactions and band topology intertwine, while the interlayer coupling plays a core role in the formation of moiré potential. However, the limited interlayer coupling strength and the lack of efficient tuning methods hinder further exploration of correlated phenomena in moiré semiconductors. We introduce a cryogenic dual-gated diamond–anvil platform using helium as a pressure medium, enabling reversible hydrostatic tuning together with magneto-optical spectroscopy in twisted bilayer WSe2. Pressure enhances the moiré potential, redshifts excitons, and stabilizes Stoner ferromagnetism otherwise absent at a 3.1° twist. Simultaneously, the half-filled C= 1 Chern insulating state strengthens, exhibiting a reduced saturation field. Moreover, we observed a topological phase transition from Chern insulator to Mott insulator at around 2 GPa. First-principles calculations reveal that a Γ–K valence band maximum switching drives this transition by converting an Ising-like topological K-valley miniband into a spin-degenerate trivial Γ miniband. Our findings demonstrate hydrostatic pressure as a powerful, continuous control axis for correlated magnetism and topological band engineering in moiré materials.

Abstract

Moiré semiconductors offer flat bands where Coulomb interactions and band topology intertwine, while the interlayer coupling plays a core role in the formation of moiré potential. However, the limited interlayer coupling strength and the lack of efficient tuning methods hinder further exploration of correlated phenomena in moiré semiconductors. We introduce a cryogenic dual-gated diamond–anvil platform using helium as a pressure medium, enabling reversible hydrostatic tuning together with magneto-optical spectroscopy in twisted bilayer WSe2. Pressure enhances the moiré potential, redshifts excitons, and stabilizes Stoner ferromagnetism otherwise absent at a 3.1° twist. Simultaneously, the half-filled C= 1 Chern insulating state strengthens, exhibiting a reduced saturation field. Moreover, we observed a topological phase transition from Chern insulator to Mott insulator at around 2 GPa. First-principles calculations reveal that a Γ–K valence band maximum switching drives this transition by converting an Ising-like topological K-valley miniband into a spin-degenerate trivial Γ miniband. Our findings demonstrate hydrostatic pressure as a powerful, continuous control axis for correlated magnetism and topological band engineering in moiré materials.

Abstract

Moiré semiconductors offer flat bands where Coulomb interactions and band topology intertwine, while the interlayer coupling plays a core role in the formation of moiré potential. However, the limited interlayer coupling strength and the lack of efficient tuning methods hinder further exploration of correlated phenomena in moiré semiconductors. We introduce a cryogenic dual-gated diamond–anvil platform using helium as a pressure medium, enabling reversible hydrostatic tuning together with magneto-optical spectroscopy in twisted bilayer WSe2. Pressure enhances the moiré potential, redshifts excitons, and stabilizes Stoner ferromagnetism otherwise absent at a 3.1° twist. Simultaneously, the half-filled C= 1 Chern insulating state strengthens, exhibiting a reduced saturation field. Moreover, we observed a topological phase transition from Chern insulator to Mott insulator at around 2 GPa. First-principles calculations reveal that a Γ–K valence band maximum switching drives this transition by converting an Ising-like topological K-valley miniband into a spin-degenerate trivial Γ miniband. Our findings demonstrate hydrostatic pressure as a powerful, continuous control axis for correlated magnetism and topological band engineering in moiré materials.

Abstract

Moiré semiconductors offer flat bands where Coulomb interactions and band topology intertwine, while the interlayer coupling plays a core role in the formation of moiré potential. However, the limited interlayer coupling strength and the lack of efficient tuning methods hinder further exploration of correlated phenomena in moiré semiconductors. We introduce a cryogenic dual-gated diamond–anvil platform using helium as a pressure medium, enabling reversible hydrostatic tuning together with magneto-optical spectroscopy in twisted bilayer WSe2. Pressure enhances the moiré potential, redshifts excitons, and stabilizes Stoner ferromagnetism otherwise absent at a 3.1° twist. Simultaneously, the half-filled C= 1 Chern insulating state strengthens, exhibiting a reduced saturation field. Moreover, we observed a topological phase transition from Chern insulator to Mott insulator at around 2 GPa. First-principles calculations reveal that a Γ–K valence band maximum switching drives this transition by converting an Ising-like topological K-valley miniband into a spin-degenerate trivial Γ miniband. Our findings demonstrate hydrostatic pressure as a powerful, continuous control axis for correlated magnetism and topological band engineering in moiré materials.