Chiral And Topological Properties Of Phonons In Special 2D Lattices

With the rapid development of the optical field,the size of the optical device is constantly shrinking,but the heat emitted by the unit area of the micro device is gradually increasing,which will seriously affect the performance of the optical device.Phonon is the energy quantum of lattice vibration,and is the main carrier of heat.The study of phonon plays an important role in heat transport,thermoelectric energy conversion and superconductivity.In this paper,phonon chirality and topological properties of Lieb lattice and Lieb-Kagome lattice are studied based on the theory and method of lattice dynamics and phononics.By constructing the dynamic matrix and equations of motion,and solving the matrix eigenvalue and eigen vector,Lieb lattice and Lieb-Kagome lattice are studied in the vibration mode of the atom,and then explores the connection between the phonon spectrum and the lattice symmetry,and the characteristics of the phonon degenerate state.By breaking time reversal symmetry,we observe the chiral phonon and nontrivial Berry curvature.The strain gradient field makes the chiral phonon with non-zero Berry curvature acquire abnormal velocity,which affects phonon transport.In Lieb lattices,chiral phonons can exist on highly symmetric paths in the Brillouin region,not limited to highly symmetric points.By studying the transition state of Lieb-Kagome lattice,we find that phonon spectrum and degeneracy point have obvious changes during the evolution from Lieb lattice to Kagome lattice.With the band gap of phonon spectrum,Berry curvature appears extreme value at corresponding special point.Magnetic field has a direct influence on chirality and topological properties,whether it is the direction of magnetic field or the magnetic field strength,which indicates that phonon properties are adjustable.For the above two lattice systems,we study their chiral phonons and topological properties,explore the relationship between these properties and lattice structure,further enrich the research content of phononics.Thus,in device design,it provides theoretical guidance for materials containing similar two-dimensional structures,increases the possibility of phonon application in the field of optics,and improves the heat-sinking capability of optical devices.