  Topological notions in physics have become a powerful perspective that leads
to the discoveries of topological interface states (TISs). In this work, we
present a scheme to achieve negative refraction by leveraging the properties of
TISs in a valley photonic crystal (VPC). Due to the chiral characteristics, one
type of the TISs deterministically possesses negative dispersion relation,
which can cause an obliquely incident wave to undergo a negative lateral shift.
By stacking multiple VPC interfaces, the TIS-induced lateral shifts can relay
in the transmitted wave towards the far side of incidence. The resultant
outgoing wave appears to have undergone negative refraction. This finding is
verified in microwave experiments. Our scheme opens new application scenarios
for topological systems in bulk wave manipulations.
