  We report phonon renormalization induced by an external electric field E in
ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)]
nanofibers through measuring the E-dependent thermal conductivity. Our
experimental results are in excellent agreement with the theoretical ones
derived from the lattice dynamics. The renormalization is attributed to the
anharmonicity that modifies the phonon spectrum when the atoms are pulled away
from their equilibrium positions by the electric field. Our finding provides an
efficient way to manipulate the thermal conductivity by tuning external fields
in ferroelectric materials.
