Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied bulk properties, while their single-layer variants have become one of the most prominent examples of two-dimensional materials beyond graphene. Their disparate ground states largely depend on transition metal d-electron-derived electronic states, on which the vast majority of attention has been concentrated to date. Here, we focus on the chalcogen-derived states. From density-functional theory calculations together with spin- and angle-resolved photoemission, we find that these generically host a co-existence of type-I and type-II three-dimensional bulk Dirac fermions as well as ladders of topological surface states and surface resonances. We demonstrate how these naturally arise within a single p-orbital manifold as a general consequence of a trigonal crystal field, and as such can be expected across a large number of compounds. Already, we demonstrate their existence in six separate TMDs, opening routes to tune, and ultimately exploit, their topological physics.

过渡金属二硫化碳（TMD）以其丰富多样的体积特性而闻名，而其单层变体已成为二维材料中石墨烯以外最突出的例子之一。它们的不同基态在很大程度上取决于过渡金属d电子衍生的电子态，迄今为止，绝大多数注意力都集中在过渡金属d电子衍生的电子态上。在这里，我们关注硫族元素衍生的状态。从密度泛函理论计算以及自旋和角度分辨的光发射，我们发现它们通常共存I型和II型三维体狄拉克费米子以及拓扑表面状态和表面的阶梯共鸣。我们演示了这些自然如何在单个p内出现-轨道流形是三角晶体场的一般结果，因此有望在大量化合物中使用。我们已经证明了它们存在于六个单独的TMD中，为调整和最终利用它们的拓扑物理开辟了道路。