  One of the main features of Weyl semimetals is the existence of Fermi arc
surface states at their surface, which cannot be realized in pure
two-dimensional systems in the absence of many-body interactions. Due to the
gapless bulk of the semimetal, it is, however, challenging to observe clear
signatures from the Fermi arc surface states. Here, we propose to detect such
novel surface states via perfect negative refraction that occurs between two
adjacent open surfaces with properly orientated Fermi arcs. Specifically, this
phenomenon visibly manifests in non-local transport measurement, where the
negative refraction generates a return peak in the real-space conductance. This
provides a unique signature of the Fermi arc surface states. We discuss the
appearance of this peak both in inversion and time-reversal symmetric Weyl
semimetals, where the latter exhibits conductance oscillations due to multiple
negative refraction scattering events.
