Electron-phonon interactions in few-septuple-layers magnetic topological insulator MnBi₂Te₄

Intrinsic magnetic topological insulators exhibit chiral edge modes and quantum anomalous Hall effect (QAH) without any external magnetic field. Such an exotic quantum state opens a new pathway for lossless energy transport. MnBi₂Te₄ (MBT), an intrinsically magnetic compound, exhibits such an exotic quantum state depending on the thickness of the septuple layers (SL). For example, 1 SL MBT is a topologically trivial ferromagnetic (FM) insulator, while 3 SL MBT is a topologically nontrivial antiferromagnetic (AFM) QAH insulator. Although the magnetic ordering can exist beyond 100 K, the QAH state can only be observed below 1 K. Due to the rise of temperature, electron-phonon interactions (EPI) play a role in the QAH state. Based on the density functional perturbation theory (DFPT), we show that EPI in MBT strongly correlate with the magnetic ordering, septuple layers thickness and electronic band topology. In particular, the electron-phonon scattering is significantly lower in the QAH state (3 SL MBT) compared to 1 SL FM, 2 SL AFM, and 2 SL FM. We also observe a thickness-dependent phonon energy shift and dynamical stability of MBT with different thicknesses.