Topological Phonons and Thermoelectric Conversion in Crystalline Materials

Topological phononics, a fascinating frontier in condensed matter physics, holds great promise for advancing energy-related applications. Topologically nontrivial phonons typically possess gapless edge or surface states. These exotic states of lattice vibrations, characterized by their nontrivial topology, offer unique opportunities for manipulating and harnessing energy transport. The exploration of topological phonons opens new avenues in understanding and controlling thermal transport properties, with potential applications in fields such as thermoelectric materials, phononic devices, and waste heat recovery. Here, an overview of concepts such as Berry curvature and topological invariants, along with the applications of phonon tight-binding method and nonequilibrium Green's function method in the field of topological phononics is provided. This review encompasses the latest research progress of various topological phonon states within crystalline materials, including topological optical phonons, topological acoustical phonons, and higher-order topological phonons. Furthermore, the study delves into the prospective applications of topological phonons in the realm of thermoelectric conversion, focusing on aspects like size effects and symmetry engineering. The complex coupling relationships between parameters in ZT provide a huge obstacle for optimizing the thermoelectric properties. The exploration of topological phonons offers unique opportunities for manipulating and harnessing energy transport. This article provides a comprehensive review of the rich topological phonon states in crystalline materials and their research methods. The prospects and limitations of these topological states in thermoelectric conversion is also discussed. image