Moiré Topology in Twisted Structures with Noncollinear Spin-Orbit Coupling

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Chemistry

Background:

• Moiré superlattices are crucial for flat bands and topological phases.
• Existing methods often rely on hexagonal lattices and valley-contrasting Berry curvature.
• A new approach is needed for broader applications.

Purpose of the Study:

• To propose a novel route to topological moiré minibands.
• To explore the use of noncollinear spin-orbit coupling (SOC) in centrosymmetric type-II SOC bilayers.
• To achieve isolated topological minibands without valley degrees of freedom or hexagonal symmetry.

Main Methods:

• Utilized interlayer hybridization to open local pseudogaps and localize Berry curvature.
• Employed twisting to reconstruct localized Berry curvature into topological minibands.
• Demonstrated the mechanism in tetragonal Dresselhaus-SOC HgI2 with a Lieb-like moiré potential.
• Developed a physics-informed machine-learning surrogate to optimize material design.

Main Results:

• Achieved topological flat bands in HgI2.
• Identified stronger SOC as a key design principle for improved miniband isolation.
• Successfully replaced Hg with Pb in PbI2 to create narrower and better-isolated minibands.
• Demonstrated support for correlation-driven magnetism and tunable quantum spin Hall and Chern insulating phases.

Conclusions:

• The proposed mechanism offers a new pathway to topological moiré minibands.
• Physics-informed machine learning accelerates the discovery of optimized materials.
• PbI2 presents a promising material realization for experimental exploration of novel quantum phenomena.