  The carrier dynamics and electronic structures of type-II Weyl semimetal
candidates MoTe$_2$ and WTe$_2$ have been investigated by using
temperature-dependent optical conductivity [$\sigma(\omega)$] spectra. Two
kinds of Drude peaks (narrow and broad) have been separately observed. The
width of the broad Drude peak increases with elevating temperature above the
Debye temperature of about 130 K in the same way as those of normal metals, on
the other hand, the narrow Drude peak becomes visible below 80 K and the width
is rapidly suppressed with decreasing temperature. Because the temperature
dependence of the narrow Drude peak is similar to that of a type-I Weyl
semimetal TaAs, it was concluded to originate from Dirac carriers of Weyl
bands. The result suggests that the conductance has the contribution of two
kinds of carriers, normal semimetallic and Dirac carriers, and this observation
is an evidence of type-II Weyl semimetals of MoTe$_2$ and WTe$_2$. The obtained
$\sigma(\omega)$ spectra in the interband transition region can be explained by
band structure calculations with a band renormalization owing to electron
correlation.
