A magnetic topological insulator, MnBi₂Te₄, exhibits a quantized anomalous Hall effect when subjected to a magnetic field. This material, with intrinsic magnetic order, is an antiferromagnet at high temperatures but becomes ferromagnetically ordered under a magnetic field. The study demonstrates that a quantized anomalous Hall effect is achieved in atomically thin MnBi₂Te₄ under a moderate magnetic field, making it the first intrinsic magnetic topological insulator to exhibit this effect. The result provides an ideal platform for exploring various topological phenomena. The discovery of topological quantum materials highlights the importance of band topology in condensed matter physics. Topological materials possess protected quantum states that are robust against local perturbations. In topological insulators, the surface states are gapless and exhibit Dirac dispersion. Introducing magnetism breaks time-reversal symmetry and opens a gap in the surface states, leading to a chiral edge mode that can give rise to a quantum anomalous Hall effect when the Fermi level is within the exchange gap. The experimental observation of the quantum anomalous Hall effect in chromium-doped (Bi,Sb)₂Te₃ represents a significant achievement in topological quantum material research. However, the random distribution of magnetic dopants in such materials limits the quality of the magnetic topological insulators. In contrast, MnBi₂Te₄ is an intrinsic magnetic topological insulator with a natural magnetic order, allowing for the study of topological effects in pristine crystals. The study investigates the quantum transport in atomically thin MnBi₂Te₄ flakes. The material is a layered ternary tetradymite compound with a structure similar to Bi₂Te₃, but with an additional Mn-Te bilayer between each quintuple layer. The material is an antiferromagnet at high temperatures but becomes ferromagnetically ordered under a magnetic field. The study shows that a moderate magnetic field can align the layers and induce a quantized anomalous Hall effect in the material. The results demonstrate that the quantized anomalous Hall effect is robust at temperatures up to 4.5 K, with a transport gap of 21 K. The study also shows that the quantized Hall effect is not due to Landau level quantization but rather to the chiral edge state within the exchange gap. The findings highlight the potential of MnBi₂Te₄ as a promising material for exploring topological quantum phenomena.A magnetic topological insulator, MnBi₂Te₄, exhibits a quantized anomalous Hall effect when subjected to a magnetic field. This material, with intrinsic magnetic order, is an antiferromagnet at high temperatures but becomes ferromagnetically ordered under a magnetic field. The study demonstrates that a quantized anomalous Hall effect is achieved in atomically thin MnBi₂Te₄ under a moderate magnetic field, making it the first intrinsic magnetic topological insulator to exhibit this effect. The result provides an ideal platform for exploring various topological phenomena. The discovery of topological quantum materials highlights the importance of band topology in condensed matter physics. Topological materials possess protected quantum states that are robust against local perturbations. In topological insulators, the surface states are gapless and exhibit Dirac dispersion. Introducing magnetism breaks time-reversal symmetry and opens a gap in the surface states, leading to a chiral edge mode that can give rise to a quantum anomalous Hall effect when the Fermi level is within the exchange gap. The experimental observation of the quantum anomalous Hall effect in chromium-doped (Bi,Sb)₂Te₃ represents a significant achievement in topological quantum material research. However, the random distribution of magnetic dopants in such materials limits the quality of the magnetic topological insulators. In contrast, MnBi₂Te₄ is an intrinsic magnetic topological insulator with a natural magnetic order, allowing for the study of topological effects in pristine crystals. The study investigates the quantum transport in atomically thin MnBi₂Te₄ flakes. The material is a layered ternary tetradymite compound with a structure similar to Bi₂Te₃, but with an additional Mn-Te bilayer between each quintuple layer. The material is an antiferromagnet at high temperatures but becomes ferromagnetically ordered under a magnetic field. The study shows that a moderate magnetic field can align the layers and induce a quantized anomalous Hall effect in the material. The results demonstrate that the quantized anomalous Hall effect is robust at temperatures up to 4.5 K, with a transport gap of 21 K. The study also shows that the quantized Hall effect is not due to Landau level quantization but rather to the chiral edge state within the exchange gap. The findings highlight the potential of MnBi₂Te₄ as a promising material for exploring topological quantum phenomena.