  The recent discovered intrinsic magnetic topological insulator MnBi2Te4 have
been met with unusual success in hosting emergent phenomena such as the quantum
anomalous Hall effect and the axion insulator states. However, the surface-bulk
correspondence of the Mn-Bi-Te family, composed by the superlattice-like
MnBi2Te4/(Bi2Te3)n (n = 0, 1, 2, 3 ...) layered structure, remains intriguing
but elusive. Here, by using scanning tunneling microscopy (STM) and
angle-resolved photoemission spectroscopy (ARPES) techniques, we unambiguously
assign the two distinct surface states of MnBi4Te7 (n = 1) to the
quintuple-layer (QL) Bi2Te3 termination and the septuple-layer (SL) MnBi2Te4
termination, respectively. A comparison of the experimental observations with
theoretical calculations reveals the diverging topological behaviors,
especially the hybridization effect between magnetic and nonmagnetic layers, on
the two terminations: a gap on the QL termination originating from the
topological surface states of the QL hybridizing with the bands of the beneath
SL, and a gapless Dirac-cone band structure on the SL termination with
time-reversal symmetry. The quasi-particle interference patterns further
confirm the topological nature of the surface states for both terminations,
continuing far above the Fermi energy. The QL termination carries a
spin-helical Dirac state with hexagonal warping, while at the SL termination, a
strongly canted helical state from the surface lies between a pair of
Rashba-split states from its neighboring layer. Our work elucidates an
unprecedented hybridization effect between the building blocks of the
topological surface states, and also reveals the termination-dependent
time-reversal symmetry breaking in a magnetic topological insulator, rendering
an ideal platform to realize the half-integer quantum Hall effect and relevant
quantum phenomena.
