  We numerically investigate stress relaxation in soft athermal disks to reveal
critical slowing down when the system approaches the jamming point. The
exponents describing the divergence of the relaxation time differ dramatically
depending on whether the transition is approached from the jammed or unjammed
phase. This contrasts sharply with conventional dynamic critical scaling
scenarios, where a single exponent characterizes both sides. We explain this
surprising difference in terms of the vibrational density of states (vDOS),
which is a key ingredient of linear viscoelastic theory. The vDOS exhibits an
extra slow mode that emerges below jamming, which we utilize to demonstrate the
anomalous exponent below jamming.
