Valley-polarized quantum anomalous Hall phases and tunable topological phase transitions in half-hydrogenated Bi honeycomb monolayers

TL;DR

This paper predicts valley-polarized quantum anomalous Hall phases with large gaps and tunable topological transitions in half-hydrogenated Bi monolayers, enabling robust valleytronics and dissipationless electronics.

Contribution

It introduces novel VP-QAH phases in Bi monolayers with large gaps and demonstrates tunable topological phase transitions driven by magnetization orientation.

Findings

Large gap of 0.19 eV in VP-QAH phases.

Reversal of magnetization switches valley and topological states.

Four distinct phases depending on magnetization direction.

Abstract

Based on first-principles calculations, we find novel valley-polarized quantum anomalous Hall (VP-QAH) phases with a large gap-0.19 eV at an appropriate buckled angle and tunable topological phase transitions driven by the spontaneous magnetization within a half-hydrogenated Bi honeycomb monolayer. Depending on the magnetization orientation, four different phases can emerge, i.e., two VP-QAH phases, ferromagnetic insulating and metallic states. When the magnetization is reversed from the +$\mathbf{z}$ to -$\mathbf{z}$ directions, accompanying with a sign change in the Chern number (from -1 to +1), the chiral edge state is moved from valley $K$ to $K'$. Our findings provide a platform for designing dissipationless electronics and valleytronics in a more robust manner through the tuning of the magnetization orientation.