  Anharmonic lattice vibrations govern the thermal dynamics in materials and
present how the atoms interact and how they conduct heat. An indepth
understanding of the microscopic mechanism of phonon anharmonicity in condensed
systems is critical for developing better functional and energy materials. In
recent years, a variety of novel behaviors in condense matters are driven by
phonon anharmonic effects in some way or another, such as soft mode phase
transition, negative thermal expansion, multiferroicity, ultralow thermal
conductivity or high thermal resistance, and high-temperature
superconductivity, etc. All these properties have endowed anharmonicity with
many promising applications and provided remarkable opportunities for
developing anharmonicity engineering, regulating heat transport towards
excellent performance in materials. In this work, we review the recent
development of the study on phonon anharmonic effect and summarize its
origination, influence and mechanism, research methods, and applications.
Besides, the remaining challenges, future trends, and prospects of phonon
anharmonicity are also put forward.
