External field-engineered tunable chern number and valley-polarized quantum anomalous hall effect in Ti 3 S 3 Te 2 monolayer

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 A 3 B 3 C 2 lattice. Using density functional theory calculations, the monolayer Ti 3 S 3 Te 2 , a candidate for the TB model, was predicted to be a robust ferromagnetic Weyl semimetal protected by C 2 x 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 Ti 3 S 3 Te 2 transitioned into a high-Chern-number QAH insulator with C = −2 under 4% or larger compressive strains. Furthermore, breaking the C 2 x T 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.