Vibrational dynamics driven by structural symmetries and complexities

Vibrational excitations and their influence on material structure and function often govern the potential for applications, such as thermoelectrics, or set limitations for these, such as spin-phonon couplings in magnetic storage and processing devices. As such, developing deep insights into the rich physics of phonons and their quasiparticle interactions is critical to developing further fundamental insights toward design of improved or new material functionalities. Here, I will discuss recent advances in our understanding of vibrational behaviors of materials, particularly highlighting the role of structural complexities and symmetries in determining vibrational dynamics and transport. More specifically, I will discuss twist phase relations in materials with screw axes, translational phase relations between primitive and conventional geometries, how such relations manifest in measured spectra, and phonon scattering behaviors in layered structures. I will discuss this physics in the context of a variety of materials, including wide-band gap compounds and superlattices [(Al/Ga)N], magnetic semiconductors [Mn(Te/Sb/Bi)], elemental metals (Te), and cleavable ferromagnets (CrCl₃).



L.L. acknowledges support from the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.