  Phonons as collective excitations of lattice vibrations are the main heat
carriers in solids. Tremendous effort has been devoted to investigate phonons
and related properties, giving rise to an intriguing field of phononics, which
is of great importance to many practical applications, including heat
dissipation, thermal barrier coating, thermoelectrics and thermal control
devices. Meanwhile, the research of topology-related physics, awarded the 2016
Nobel Prize in Physics, has led to discoveries of various exotic quantum states
of matter, including the quantum (anomalous/spin) Hall [Q(A/S)H] effects,
topological insulators/semimetals and topological superconductors. An emerging
research field is to bring topological concepts for a new paradigm
phononics---"topological phononics". In this Perspective, we will briefly
introduce this emerging field and discuss the use of novel quantum degrees of
freedom like the Berry phase and topology for manipulating phonons in
unprecedentedly new ways.
