  The fermionic Shastry-Sutherland model has a rich phase diagram, including
phases with massless Dirac fermions, a quadratic band crossing point, and a
pseudospin-1 Weyl fermion. Berry phases defined by the one-dimensional momentum
as a parameter are quantized into 0 or pi due to the inversion symmetry
combined with the time reversal, or existence of the glide plane, which also
protects the massless Dirac cones with continuous parameters. This is the
symmetry protected Z2 quantization. We have further demonstrated the Z2 Berry
phases generically determine the existence of edge states in various phases and
with different types of the boundaries as the bulk-edge correspondence of the
massless Dirac fermion systems.
