A family tree of two-dimensional magnetic materials with tunable topological properties

TL;DR

This paper predicts a family of 2D magnetic materials with tunable topological properties, expanding the potential for exotic quantum states and applications in spintronics.

Contribution

It introduces a design principle for converting trivial 2D ferromagnetic insulators into topological systems via atomic substitutions, supported by first-principles calculations.

Findings

CrI3 derivatives become high-temperature quantum anomalous Hall insulators.

CrBr3 derivatives become topological half-metals.

The materials are easily exfoliable from bulk forms.

Abstract

Two-dimensional (2D) magnetic materials empowered with nontrivial band topology may lead to the emergence of exotic quantum states with significant application potentials. Here we predict a family tree of 2D magnetic materials with tunable topological properties, starting from the parental materials of CrI3 and CrBr3. The underlying design principle is that, by substituting the alternating sites of the Cr honeycomb lattice sandwiched between the halogen layers with V or Mn, the parental materials of trivial ferromagnetic insulators are ripe to be converted into topological systems. Specifically, our first-principles calculations show that, due to the elegant interplay between bandgap narrowing and spin-orbital coupling, CrI3 branches into high-temperature quantum anomalous Hall insulators of CrVI6 and CrMnI6 with different topological invariants, while CrBr3 branches into topological half-metals of CrVBr6 and CrMnBr6. Those novel 2D magnets are also shown to be easily exfoliated from their bulk counterparts. The present study is thus geared to advance the field of 2D magnetic materials into the topologically nontrivial realm.