标题： 弗洛凯复合狄拉克半金属 显示英文标题

标题： Floquet composite Dirac semimetals

摘要： 狄拉克半金属根据其狄拉克点的拓扑电荷被分为I型、II型和III型。 如果一个三维（3D）系统可以被切分成一族依赖于$k_z$的正常和拓扑绝缘体，I型狄拉克点将二维正常绝缘体与二维一阶拓扑绝缘体分隔开，而II型（III型）狄拉克点将二维正常（一阶）绝缘体与二维二阶拓扑绝缘体分隔开。 为了研究不同狄拉克点相互作用产生的效应，人们可能会想知道这些狄拉克点是否可以在单一系统中共存。 在这里，我们提出一种方案，在具有时间反演和空间反演对称性的弗洛凯四带系统中诱导复合狄拉克半金属。 建立了一种通用描述来表征弗洛凯系统中的狄拉克半金属。 结果表明，通过δ函数或谐波驱动可以诱导出同时包含I型、II型和III型狄拉克点的狄拉克半金属。 我们的结果为探索新型狄拉克半金属提供了一个有前景的新途径。 显示英文摘要

摘要： Dirac semimetals are classified into types I, II, and III based on the topological charge of their Dirac points. If a three-dimensional (3D) system can be sliced into a family of $k_z$-dependent normal and topological insulators, type I Dirac points separate a 2D normal insulator from a 2D first-order topological insulator, while type II (III) Dirac points separate a 2D normal (first-order) insulator from a 2D second-order topological insulator. To investigate the effects arising from the interplay of distinct Dirac points, one may wonder whether these Dirac points can coexist in single system. Here, we propose a scheme to induce composite Dirac semimetals in a Floquet four-band system with time-reversal and space-inversion symmetries. A general description is established to characterize Dirac semimetals in Floquet systems. The results show that Dirac semimetals hosting coexisting type I, II, and III Dirac points can be induced by delta-function or harmonic driving. Our results provide a promising new avenue for exploring novel Dirac semimetals.