  Exotic properties in single or few layers of van der Waals materials carry
great promise for applications in nanoscaled electronics, optoelectronics and
flexible devices. The established, distinct examples include extremely high
mobility and superior thermal conductivity in graphene, a large direct band gap
in monolayer MoS2 and quantum spin Hall effect in WTe2 monolayer, etc. All
these exotic properties arise from the electron quantum confinement effect in
the two-dimensional limit. Here we report a novel phenomenon due to
one-dimensional (1D) confinement of carriers in a layered van der Waals
material NbSi0.45Te2 revealed by angle-resolved photoemission spectroscopy,
i.e. directional massless Dirac fermions. The 1D behavior of the carriers is
directly related to a stripe-like structural modulation with the long-range
translational symmetry only along the stripe direction, as perceived by
scanning tunneling microscopy experiment. The four-fold degenerated node of 1D
Dirac dispersion is essential and independent on band inversion, because of the
protection by nonsymmorphic symmetry of the stripe structure. Our study not
only provides a playground for investigating the striking properties of the
essential directional massless Dirac fermions, but also introduces a unique
monomer with 1D long-range order for engineering nano-electronic devices based
on heterostructures of layered van der Waals materials.
