  In graphene, the pseudospin and the valley flavor arise as new types of
quantum degrees of freedom due to the honeycomb lattice comprising two
sublattices (A and B) and two inequivalent Dirac points (K and K') in the
Brillouin zone, respectively. Unique electronic properties of graphene result
in striking phenomena such as Klein tunnelling, Veselago lens, and
valley-polarized currents. Here, we investigate the roles of the pseudospin and
the valley in electron scattering at graphene edges and show that they are
strongly correlated with charge density modulations of short-wavelength
oscillations and slowly-decaying beat patterns. Theoretical analyses using
nearest-neighbor tight-binding methods and first-principles density-functional
theory calculations agree well with our experimental data from the scanning
tunneling microscopy. We believe that this study will lead to useful
application of graphene to "valleytronics" and "pseudospintronics".
