Altermagnetism Induced Topological Phase Transitions in Kane-Mele Model

TL;DR

This paper theoretically shows that applying d-wave altermagnetism to the Kane-Mele topological insulator induces tunable quantum anomalous Hall effects and second-order topological insulator phases, revealing new topological phase transitions.

Contribution

It introduces the concept of using altermagnetism to induce and control diverse topological phases in the Kane-Mele model, expanding the understanding of magnetic effects on topological materials.

Findings

Altermagnetism induces second-order topological insulators with corner states.

Rashba spin-orbit coupling enables transition to QAHE with various Chern numbers.

QAHE with mixed chirality observed, featuring counter-propagating edge modes.

Abstract

We theoretically demonstrate that Chern number tunable quantum anomalous Hall effect (QAHE) and second-order topological insulators can be induced in the two-dimensional $\mathbb{Z}_2$ topological insulator (TI), i.e., Kane-Mele model, by applying $d$-wave altermagnetism. When the N\'eel vector of altermagentism lies in the $x-y$ plane, the $\mathbb{Z}_2$ TI is broken and driven into a second-order topological insulator phase, exhibiting the representative corner states at nanoflakes. When the intrinsic Rashba spin-orbit coupling is further included, the second-order TI is further driven into the QAHE phase with various Chern numbers (e.g., $\mathcal{C}=\pm1$ or $\pm3$). When the N\'eel vector is along $z$ direction, the intrinsic Rashba spin-orbit coupling is necessary to break the mirror symmetry to allow a sequential emergence of second-order TI and QAHE along with the increase of altermagentism strength. We also observe the QAHE with mixed-chirality, i.e., there exist counter-propagating edge modes but net chiral current at the ribbon boundary. Our work shows that altermagnetism can play a crucial role in exploring a rich variety of topological phases, just like its counterparts of ferromagnetism and antiferromagnetism.