  Spin- and charge-lattice interactions are potential key factors in the
microscopic mechanism of high-temperature superconductivity in cuprates.
Although both interactions can dramatically shape the low-energy electronic
structure, their phenomenological roles in superconductivity are usually
investigated independently. Employing angle-resolved photoemission
spectroscopy, we reveal the spectroscopic fingerprint of short-range
antiferromagnetic order in conjunction with enhanced electron-phonon
interaction in the electron-doped cuprate superconductor
$\mathrm{Nd_{1.85}Ce_{0.15}CuO_4}$. The observed mode coupling exhibits a
strong momentum dependence that is in striking contrast to the node-antinode
dichotomy previously observed in the hole-doped cuprates. Our results reveal an
intimate relationship between electron-phonon coupling and antiferromagnetic
fluctuations, which collectively sets the stage for unconventional
superconductivity in the electron-doped cuprates.
