  Doped antiferromagnets host a vast array of physical properties and learning
how to control them is one of the biggest challenges of condensed matter
physics. La$_{1.7}$Sr$_{0.3}$NiO$_4$ (LSNO) is a classic example of such a
material. At low temperatures holes introduced via substitution of La by Sr
segregate into lines to form boundaries between magnetically ordered domains in
the form of stripes. The stripes become dynamic at high temperatures, but LSNO
remains insulating presumably because an interplay between magnetic
correlations and electron-phonon coupling localizes charge carriers. Magnetic
degrees of freedom have been extensively investigated in this system, but
phonons are almost completely unexplored. We searched for electron-phonon
anomalies in LSNO by inelastic neutron scattering. Giant renormalization of
plane Ni-O bond-stretching modes that modulate the volume around Ni appears on
entering the dynamic charge stripe phase. Other phonons are a lot less
sensitive to stripe melting. Dramatic overdamping of the breathing modes
indicates that dynamic stripe phase may host small polarons. We argue that this
feature sets electron-phonon coupling in nickelates apart from that in cuprates
where breathing phonons are not overdamped and point out remarkable
similarities with the colossal magnetoresistance (CMR) manganites.
