Flux states and topological phases from spontaneous time-reversal symmetry breaking in CrSi(Ge)Te$_3$-based systems

TL;DR

This study predicts that adatom-covered CrSiTe3 and CrGeTe3 monolayers can host flux states with nontrivial topological properties arising from spontaneous time-reversal symmetry breaking, even without spin-orbit coupling.

Contribution

It demonstrates the emergence of flux states and topological phases in CrSiTe3 and CrGeTe3 monolayers due to nonlocal Coulomb interactions, a novel mechanism for topological phenomena.

Findings

Flux states induce antiferromagnetic orbital moments.

Chern numbers of ±1 predicted without spin-orbit coupling.

Large energy gaps (~100 meV) associated with topological phases.

Abstract

We study adatom-covered single layers of CrSiTe$_3$ and CrGeTe$_3$ using first-principles calculations based on hybrid functionals. We find that the insulating ground state of a monolayer of La (Lu) deposited on single-layer CrSiTe$_3$ (CrGeTe$_3$) carries spontaneously generated current loops around the Cr sites, These "flux states" induce antiferromagnetically ordered orbital moments on the Cr sites and are also associated with nontrivial topological properties. The calculated Chern numbers for these systems are predicted to be $\pm 1$ even in the absence of spin-orbit coupling, with sizable gaps on the order of 100 meV. The flux states and the associated topological phases result from spontaneous time-reversal symmetry breaking due to the presence of nonlocal Coulomb interactions.