  Very recently, a new two-dimensional graphene-like topological insulator,
Bi14Rh3I9, has been synthesized. The Bi-Rh sheets with a strong spin-orbit
interaction are graphene analogues with a honeycomb net composed of RhBi8
cubes. Here we derive the low-energy effective Hamiltonian involving spin-orbit
coupling for Bi14Rh3I9. In the absence of spin-orbit coupling, the Bi-Rh sheets
show two inequivalent Dirac cones at the corners of the hexagonal Brillouin
zone. The spin-orbit interaction opens a 2400 K bandgap at the Dirac points and
establishes the quantum spin Hall effect in the Bi-Rh sheets. Our result
indicates that the Bi14Rh3I9 may combine many unique electronic properties of
graphene and topological insulators, and it should host a combination of
quantum valley and spin Hall effects.
