Tunable magnetic topological insulating phases in monolayer CrI3

Abstract

We present results indicating that Chern insulator states can be achieved in the recently synthesized pristine chromium triiodide (${\mathrm{CrI}}_{3}$) by either electron or hole doping. Our first-principles density-functional-theory calculations confirmed that monolayer ${\mathrm{CrI}}_{3}$ show nontrivial Chern number $C$ in both the valence and conduction bands. By introducing on-site Coulomb interaction or epitaxial strain, the doped ${\mathrm{CrI}}_{3}$ exhibit a series of topological quantum phase transitions between multiple Chern insulator phases as well as semimetal-to-insulator transitions. We show that the covalency of Cr $d$-I $p$ bands controlled by the on-site Coulomb interaction $U$ and strain is one of the key ingredients determining the topological phase and semimetal-insulator phase boundary.