Floquet composite Dirac semimetals

TL;DR

This paper proposes a Floquet engineering scheme to create composite Dirac semimetals with coexisting types I, II, and III Dirac points, expanding the possibilities for novel topological phases in driven systems.

Contribution

It introduces a method to induce and characterize composite Dirac semimetals with multiple Dirac point types via Floquet driving while preserving symmetries.

Findings

Coexistence of type I, II, and III Dirac points demonstrated in Floquet systems.

Both delta-function and harmonic driving can realize these composite semimetals.

Provides a general framework for analyzing Dirac semimetals in periodically driven systems.

Abstract

Dirac semimetals can be 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 kz-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 a single system. Here, we propose a scheme to induce composite Dirac semimetals by a special Floquet driving that preserves 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.