  In this paper, the structural, electronic, mechanical and optical properties
of antimonene-bismuthene Van-der Waals heterostructure (Sb-Bi HS) were
calculated based on the first principle density functional theory. We explored
different stacks of Sb-Bi HS to find the most and the least stable staking for
this heterostructure. At the GGA level of theory, the most stable model is a
semiconductor with an indirect band gap of 159 meV. However, when the
spin-orbit (SO) interaction is considered, the VBM and CBM touch the Fermi
level and the HS becomes a semimetal. Our results also show that the electronic
properties of the HS are robust against the external electric field and biaxial
strain. Young modulus was calculated as 64.3N/M which predicts this HS as a
resistant material against being stretched or compressed.
  The calculated optical properties, similar to monolayer antimonene, are
completely dependent on the polarization of incident light and differ when
parallel or perpendicular polarization is considered. Moreover, the absorption
coefficient for perpendicular polarization in the visible region is
significantly increased in comparison with the monolayer antimonene. High
structural stability, electronic and mechanical robustness against electric
field and strain, along with polarization-dependent optical properties of this
HS, promise for its applications in beam splitters and nano-scale mirrors.
