  Inspired by the theoretical prediction [Phys. Rev. Lett. 86, 3423 (2001)] and
the disputed experimental results [Phys. Rev. Lett. 89, 189601(2002), Phys.
Rev. Lett. 90, 014302 (2003)], we systematically investigate the pattern of
binary mixtures consisting of same layer-thickness under vertical vibration.
Various kinds of mixtures with different diameters and densities particles are
used to observe the separation regime. It is found that these mixtures behave
like five kinds of segregation patterns for different driving control
parameters, i.e., Brazil nut (BN), reversed Brazil nut (RBN), Mixed states,
light-BN (LBN), and light-RBN (LRBN), where the latter two regimes are neither
purely segregated nor completely mixed states. Not only that, but LBN (LRBN) is
observed to be the transition path from BN (RBN) to Mixed state. Moreover, BN
phenomenon takes place in the area of low density ratio and found to be
independent of layer structure, while RBN is sensitive to the layer structure
and occurs at the large density ratio but lower diameter ratio. Our result may
be helpful for the establishment of theory about the segregation and mixing of
granular mixtures.
