Large Valley Splitting and Enhancement of Curie Temperature in a Two-Dimensional VI3/CrI3 Heterostructure

The study on two-dimensional (2D) magnetic materials attracts extensive research interest. Nonetheless, it is rare to find reports on heterostructures. Thus, we investigated the magnetic properties of a 2D VI3/CrI3 heterostructure under the external pressure. Without spin-orbit coupling (SOC), VI3/CrI3 had a direct band gap of 0.91 eV, and an indirect band gap of 0.98 eV appeared at 1.65 GPa. With SOC, the band gap was decreased to 0.56 eV, and the direct band gap feature remained even under the pressure. We obtained a perpendicular magnetic anisotropy energy of 0.4 meV/cell, and the major contribution originated from the interface iodine atoms. We also found a Curie temperature of 90 K, and this is almost twice the monolayer structures of both VI3 and CrI3. Besides, we found a large valley splitting of 21 meV, and this was further enhanced to 28 meV at 1.65 GPa. Particularly, the conduction band minimum and valence band maximum appeared in two different layers. This may suggest that a relatively long lifetime valley exciton can be observed in this VI3/CrI3 heterostructure bilayer.