Weyl phonons in condensed matter: a first-principles perspective

Abstract Weyl phonons (WPs), which simultaneously possess topological and chiral degrees of freedom, have attracted increasing attention in recent years. Based on their topological charge, dispersion characteristics, and symmetry protection mechanisms, Weyl points can be classified into conventional and unconventional types. In this review, we first introduce the research background of WPs, tracing their development from studies on Weyl semimetals. We then present a selection of representative first-principles studies on WPs, following a progression from conventional single WPs to unconventional multi-WPs, including quadratic WPs, triple WPs, and charge-four WPs. Finally, we provide an outlook on future research directions, including their potential impact on thermal transport and phononic device applications. We hope this review serves as a comprehensive guide for current research on WPs and provides insights into the rich topological structures emerging in phononic systems.