  Quantum spin Hall insulators have one-dimensional (1D) spin-momentum locked
topological edge states (ES) inside the bulk band gap, which can serve as
dissipationless channels for the practical applications in low consumption
electronics and high performance spintronics. However, the clean and atomically
sharp ES serving as ideal 1D conducting channels are still lack. Here, we
report the formation of the quasi-1D Bi4I4 nanoribbons on the surface of
Bi(111) with the support of the graphene-terminated 6H-SiC(0001) and the direct
observations of the topological ES at the step edge by scanning tunneling
microscopy and spectroscopic-imaging results. The ES reside surround the edge
of Bi4I4 nanoribbons and exhibits remarkable robustness against non time
reversal symmetry perturbations. The theoretical simulations verify the
topological non-trivial character of 1D ES, which is retained after considering
the presence of the underlying Bi(111). Our study supports the existence of
topological ES in Bi4I4 nanoribbons, paving the way to engineer the novel
topological features by using the nanoribbons as the 1D building block.
