External field-engineered tunable chern number and valley-polarized quantum anomalous hall effect in Ti3S3Te2 monolayer

Abstract

Quantum anomalous Hall (QAH) insulators with tunable Chern numbers have excellent application prospects in spintronics. Based on the eight-band tight-binding (TB) model, we realized a Chern number tunable QAH phase and valley-polarization quantum anomalous Hall (VP-QAH) state in the A₃B₃C₂ lattice. Using density functional theory calculations, the monolayer Ti₃S₃Te₂, a candidate for the TB model, was predicted to be a robust ferromagnetic Weyl semimetal protected by C_2x rotation symmetry. When the spin–orbital-coupling effect was included, the Weyl point was gapped, resulting in a QAH phase with a Chern number C = 1. Specifically, the monolayer Ti₃S₃Te₂ transitioned into a high-Chern-number QAH insulator with C = −2 under 4% or larger compressive strains. Furthermore, breaking the C_2xT rotation symmetry by applying an external electric field led to the VP-QAH state. Our work provides a promising candidate for the QAH state with a tunable Chern number and VP-QAH state, making it suitable for use in spintronic devices.