Title: Negative refraction in Weyl semimetals,
Abstract: We theoretically propose that Weyl semimetals may exhibit negative refraction
at some frequencies close to the plasmon frequency, allowing transverse
magnetic (TM) electromagnetic waves with frequencies smaller than the plasmon
frequency to propagate in the Weyl semimetals. The idea is justified by the
calculation of reflection spectra, in which \textit{negative} refractive index
at such frequencies gives physically correct spectra. In this case, a TM
electromagnetic wave incident to the surface of the Weyl semimetal will be bent
with a negative angle of refraction. We argue that the negative refractive
index at the specified frequencies of the electromagnetic wave is required to
conserve the energy of the wave, in which the incident energy should propagate
away from the point of incidence.