Ballistically propagating topologically protected states harbor exotic
transport phenomena of wide interest. Here we describe a nontopological
mechanism that produces such states at the surfaces of generic Dirac materials,
giving rise to propagating surface modes with energies near the bulk band
crossing. The robustness of surface states originates from the unique
properties of Dirac-Bloch wavefunctions which exhibit strong coupling to
generic boundaries. Surface states, described by Jackiw-Rebbi-type bound
states, feature a number of interesting properties. Mode dispersion is gate
tunable, exhibiting a wide variety of different regimes, including
nondispersing flat bands and linear crossings within the bulk bandgap. The
ballistic wavelike character of these states resembles the properties of
topologically protected states; however, it requires neither topological
restrictions nor additional crystal symmetries. The Dirac surface states are
weakly sensitive to surface disorder and can dominate edge transport at the
energies near the Dirac point.Comment: 16 pages, 4 figure
