Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone

Materials that possess nontrivial topology and magnetism is known to exhibit exotic quantum phenomena such as the quantum anomalous Hall effect. Here, we fabricate a novel magnetic topological heterostructure Mn₄Bi₂Te₇/Bi₂Te₃ where multiple magnetic layers are inserted into the topmost quintuple layer of the original topological insulator Bi₂Te₃. A massive Dirac cone (DC) with a gap of 40-75 meV at 16 K is observed. By tracing the temperature evolution, this gap is shown to gradually decrease with increasing temperature and a blunt transition from a massive to a massless DC occurs around 200-250 K. Structural analysis shows that the samples also contain MnBi₂Te₄/Bi₂Te₃. Magnetic measurements show that there are two distinct Mn components in the system that corresponds to the two heterostructures; MnBi₂Te₄/Bi₂Te₃ is paramagnetic at 6 K while Mn₄Bi₂Te₇/Bi₂Te₃ is ferromagnetic with a negative hysteresis (critical temperature  ~20 K). This novel heterostructure is potentially important for future device applications.