  Phonon localization is a phenomenon that influences numerous material
properties in condensed matter physics. Anderson localization brings rise to
localized atomic-scale phonon interferences in disordered lattices with an
influence limited to high-frequency phonons having wavelengths comparable to
the size of a randomly perturbed unit cell. Here we theoretically reveal a new
form of phonon localization induced by augmenting a crystalline material with
intrinsic phonon nanoresonators with feature sizes that can be smaller or
larger than the phonon wavelengths but must be relatively small compared to the
phonon mean free paths. This mechanism is deterministic and takes place within
numerous discrete narrow-frequency bands spread throughout the full spectrum
with central frequencies controlled by design. For demonstration, we run
molecular dynamics simulations of all-silicon nanopillared membranes at room
temperature, and apply to the underlying thermalized environment narrowband
wave packets as an excitation at precisely the frequencies where resonant
hybridizations are evident in the anharmonic phonon band structure. Upon
comparison to other frequency ranges where the nanostructure does not exhibit
local resonances, significant intrinsic spatial phonon localization along the
direction of transport is explicitly observed. Furthermore, the energy exchange
with external sources is minimized at the resonant frequencies. We conclude by
making a direct comparison with Anderson localization highlighting the
superiority of the resonant phonons across both sides of the interference
frequency limit.
