  We study correlations of non-affine displacement during simple shear
deformation of Cu-Zr bulk metallic glasses in molecular dynamics calculations.
In the elastic regime, our calculations show exponential correlation with a
decay length that we interpret as the size of a shear transformation zone in
the elastic regime. This correlation length becomes system-size dependent
beyond the yield transition as our calculation develops a shear band,
indicative of a diverging length scale. We interpret these observations in the
context of a recent proposition of yield as a first-order phase transition.
