Angle-resolved photoemission spectroscopy study of magnetic topological insulator candidates of Ce-doped Bi2–xCexSe3.

The electronic structures of the magnetic topological insulator candidates of Ce-substituted Bi_2–xCe_xSe₃ (x ≤ 0.12) have been investigated through angle-resolved photoemission spectroscopy (ARPES), soft X-ray absorption spectroscopy (XAS), and soft X-ray magnetic circular dichroism (XMCD) measurements on high-quality single crystals. Ce 3d XAS and XMCD measurements provide evidence that the substituted Ce ions in Bi_2–xCe_xSe₃ are trivalent and magnetic, confirming the purely magnetic effect of the Ce-substitution. ARPES measurements reveal the formation of an energy gap (Δ) for x > 0, indicating that the finite Δ arises from the broken time-reversal symmetry due to the substituted magnetic Ce impurities. [ABSTRACT FROM AUTHOR]