Coexistence of Electronic and Phononic Dirac Points in TiB 2 Monolayer with Inverse Sandwich Motif

作者：Shukai Wang, Shuaiyu Wang, Rong Liu, Linwei Sai, Lei Wang, Fengyu Li · 发表于：The Journal of Physical Chemistry C · 年份：2023 · DOI：10.1021/acs.jpcc.3c02778 · 被引用次数：9 · 研究领域：Graphene research and applications、Topological Materials and Phenomena、Boron and Carbon Nanomaterials Research

Although many Dirac semimetals (DSMs) have been theoretically proposed, the ideal Dirac fermions coexisting with Dirac phonons in a DSM are rare. In this work, we proposed a general strategy to assemble two-dimensional (2D) ideal DSMs using the cluster of transition metal boride with an inverse sandwich configuration. We illustrated this strategy using first-principles calculations, resulting in the creation of a 2D titanium diboride named 2 c -TiB 2 with a space group of P 2 1 / c . This monolayer was found to be thermodynamically, dynamically, and thermally stable. Additionally, it was revealed to be a DSM with an ideal Dirac cone at the Fermi level, and its topology arises from the band inversion between the p z orbitals of B atoms and d x 2 – y 2 orbitals of Ti atoms. Furthermore, the monolayer exhibits intersecting Dirac phonons along high-symmetry path Γ–X. The quantized Berry phase, inversed eigenvalues, and apparent electronic and phononic topological edge states all served as further evidence of the topological protection originating from C 2 x symmetry. The theoretical investigation into inverse sandwich structured boride monolayer not only predicts the coexistence of Dirac fermions and Dirac phonons in 2D TiB 2, but also provides a novel approach to design topological states in 2D nanomaterials.