Anomalous Landau quantization in intrinsic magnetic topological insulators

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Intrinsic magnetic topological insulators like MnBi$_{2}$Te$_{4}$ exhibit Weyl semimetal properties.
• The layer-dependent Chern number is a key characteristic of the Weyl state.
• Previous studies on MnBi$_{2}$Te$_{4}$ thin films hinted at higher Chern states but lacked clear interpretation.

Purpose of the Study:

• To investigate and achieve a tunable layer-dependent Chern number state in Mn(Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{4}$.
• To provide a clearer understanding of higher Chern states in magnetic topological insulators.
• To correlate experimental findings with theoretical calculations of Weyl point separation.

Main Methods:

• Fabrication and characterization of dual-gated Mn(Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{4}$ devices.
• Detailed analysis of quantum states under strong magnetic fields.
• Comparison of experimental data with theoretical models of Landau level spectra.

Main Results:

• A tunable layer-dependent Chern number ($C=1$) state was achieved through Sb substitution in Mn(Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{4}$.
• Experimental results are consistent with calculations of bulk Weyl point separation in doped thin films.
• Observed Hall quantization plateaus in thicker films are explained by spin-polarized Landau level spectra.

Conclusions:

• Sb substitution offers a method to tune the Chern number in intrinsic magnetic topological insulators.
• The study clarifies the nature of higher Chern states, resolving ambiguities from surface Landau levels.
• The findings contribute to the understanding of thin film magnetic topological insulators and their potential applications.