  Theoretical and experimental studies agree that
$\text{Bi}_{1-x}\text{Sb}_{x}$ ($0.07 \leq x \leq 0.21$) to be a
three-dimensional topological insulator. However, there is still a debate on
the corresponding $\text{Bi}_{1-x}\text{Sb}_{x}$(111) surface band structure.
While three spin polarized bands have been claimed experimentally,
theoretically, only two surface bands appear, with the third band being
attributed to surface imperfections. Here, we address this controversy using
angle-resolved photoemission spectroscopy (ARPES) on
$\text{Bi}_{1-x}\text{Sb}_{x}$ films. To minimize surface imperfections, we
have optimized the sample growth recipe. We have measured the evolution of the
surface band structure of $\text{Bi}_{1-x}\text{Sb}_{x}$ with $x$ increasing
gradually from $x = 0$ to $x = 0.6$. Our ARPES data show better agreement with
the theoretical calculations, where the system is topologically non-trivial
with two surface bands.

Mesoscale and Nanoscale Physics