  Coupled linear Boltzmann transport and hydrodynamic (CoLBT-hydro) model has
been developed for simultaneous simulations of jet propagation and jet-induced
medium excitation in heavy-ion collisions. Within this coupled approach, the
final reconstructed jets in heavy-ion collisions include not only hadrons from
the hadronization of medium modified jet shower partons from the linear
Boltzmann transport (LBT) but also hadrons from the freeze-out of the
jet-induced medium excitation in the hydrodynamic evolution of the bulk medium.
Using the CoLBT-hydro model, we study medium modification of the fragmentation
functions of $\gamma$-triggered jets in high-energy heavy-ion collisions at the
Large Hadron Collider. The CoLBT-hydro model is shown to describe the
experimental data not only on the suppression of leading hadrons within the jet
cone at large momentum fraction $z_\gamma=p_T^h/p_T^\gamma$ relative to the
transverse momentum of the trigger photon due to parton energy loss but also
the enhancement of soft hadrons at small $z_\gamma$ and $z_{\rm
jet}=p_T^h/p_T^{\rm jet}$ due to jet-induced medium excitation. There is no
suppression of the fragmentation function, however, at large momentum fraction
$z_{\rm jet}$ relative to the transverse momentum of the reconstructed jet due
to trigger bias and medium modification of quark to gluon jet fraction. For
jets whose final transverse momenta are comparable to or larger than that of
the trigger photon, the trigger bias can lead to enhancement of the jet
fragmentation function at large $z_{\rm jet}$.
