  Plastic deformation in metallic glasses at room temperature leads to the
development of shear bands due to shear localization. In many experiments,
shear bands have shown local density variations along their path, with a
distinct imbalance in magnitude between local densification and dilation.
However, a comprehensive mechanistic understanding or theory to explain this
asymmetry has been lacking until now. Here, we introduce a new model that
consists of a sequential arrangement of alternating topological 'charges',
generating a dipolar field. The resulting microscopic displacement field, when
integrated into the deformation gradient tensor, provides an accurate
analytical solution for the observed imbalances in the density variations. The
implications of this method are discussed, highlighting the potential to
elucidate a broader range of observations in shear bands.
