Electrically Induced Topological Chirality Switching in Orbital-Engineered Covalent Organic Radical Framework Monolayers.

Abstract

Engineering the topological properties of a quantum anomalous Hall (QAH) insulator is crucial for advancing spintronics and quantum devices. Conventional methods relying on external magnetic fields face limitations in their scalability and energy efficiency. Here, we present the realization of bipolar topological magnetic semiconductor (BTMS) using two-dimensional covalent organic radical frameworks (2D CORFs) based on an orbital-engineering approach. These BTMS host spin-polarized Dirac cones and flat bands with opposite Chern numbers, enabling electrically driven chiral switching of the QAH phase. The triacene(TRI)-CORFs achieve reversible transitions between nontrivial flat-band insulators and QAH phase via carrier doping or heteroatom substitution (e.g., N/B doping), while maintaining robust room-temperature ferromagnetism (TC ≈ 508 K), where the chirality inversion of edge currents is confirmed by Berry curvature analysis. This work establishes 2D CORFs as a versatile platform for electrically tunable topological quantum devices, bridging the gap between organic chemistry and chiral spintronics.