Photoninduced Weyl half-metal phase and spin filter effect from topological Dirac semimetals

Abstract

Recently discovered Dirac semimetals (DSMs) with two Dirac nodes, such as Na${}_3$Bi and Cd${}_2$As${}_3$, are regarded to carry the ${\mathbb{Z}}_2$ topological charge in addition to the chiral charge. Here, we study the Floquet phase transition of ${\mathbb{Z}}_2$ topological DSMs subjected to a beam of circularly polarized light. Due to the resulting interplay of the chiral and ${\mathbb{Z}}_2$ charges, the Weyl nodes are not only chirality-dependent but also spin-dependent, which constrains the behaviors in creation and annihilation of the Weyl nodes in pair. Interestingly, we find a novel phase: One spinband is in Weyl semimetal phase while the other spinband is in insulator phase, and we dub it Weyl half-metal (WHM) phase. We further study the spin-dependent transport in a Dirac-Weyl semimetal junction and find a spin filter effect as a fingerprint of existence of the WHM phase. The proposed spin filter effect, based on the WHM bulk band, is highly tunable in a broad parameter regime and robust against magnetic disorder, which is expected to overcome the shortcomings of the previously proposed spin filter based on the topological edge/surface states. Our results offer a unique opportunity to explore the potential applications of topological DSMs in spintronics.

6 pages, 4 figures

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• Valley filter and valley valve in graphene
• Quantum interference and Klein tunneling in graphene heterojunctions
• Classification of stable three-dimensional Dirac semimetals with nontrivial topology
• Evidence of Klein tunneling in graphene p-n junctions
• Disorder-induced Floquet Topological Insulators
• Dirac semimetals $A_{3}Bi$ ($A$=Na,K,Rb) as $Z_2$ Weyl semimetals

Cited by in corpus (3)

• Double exceptional links in a three-dimensional dissipative cold atomic gas
• Electrically tunable Kondo effect as a direct measurement of the chiral anomaly in disorder Weyl semimetals
• Conservation of chirality at a junction between two Weyl semimetals