Experimental Evidence of a Dirac Gap Opening in Carbon-Doped Topological Insulator Bi2Se3

Magnetic topological insulators (TIs) are promising candidates for realizing the quantum anomalous Hall effect (QAHE) and advancing the development of next-generation low-energy transistors and electronic devices. Doping Bi2Se3with nano-carbon can introduce magnetic order and open the Dirac gap without introducing extrinsic magnetic impurities. In this work, the C0.06Bi2Se3single crystal was prepared using the Bridgman method, and their electrical and magnetotransport properties were systematically investigated. Temperature-dependent resistivity and magnetoresistance measurements revealed a magnetic-field-induced metal–insulator-like transition near 152 K. Angle-resolved photoemission spectroscopy (ARPES) detected an energy gap of about 43 meV at the Dirac point, confirming that carbon doping modulates the surface state and opens the gap. Pronounced Shubnikov–de Haas oscillations indicate high carrier mobility in C0.06Bi2Se3. Furthermore, the temperature-dependent Kerr spectra shows that the spin relaxation behavior of C0.06Bi2Se3differs significantly from that of pure Bi2Se3; the relaxation process of spin electrons from the surface state (τs) dominates the spin dynamics and exhibits distinct trends around 30 K and 150 K due to the interplay of the Dirac gap and impurity-induced states. These results demonstrate the potential of magnetic topological insulator C0.06Bi2Se3for novel electronic and spintronic applications.