Topological kink states in graphene

Abstract

Due to the unique band structure, graphene exhibits a number of exotic electronic properties that have not been observed in other materials. Among them, it has been demonstrated that there exist the one-dimensional valley-polarized topological kink states localized in the vicinity of the domain wall of graphene systems, where a bulk energy gap opens due to the inversion symmetry breaking. Notably, the valley-momentum locking nature makes the topological kink states attractive to the property manipulation in valleytronics. This paper systematically reviews both the theoretical research and experimental progress on topological kink states in monolayer graphene, bilayer graphene and graphene-like classical wave systems. Besides, various applications of topological kink states, including the valley filter, current partition, current manipulation, Majorana zero modes and etc, are also introduced.

Valley filtering and valley-polarized collective modes in bulk graphene monolayers

“…Various applications of topological kink states were reviewed in Ref. [48]. In a two-terminal graphene system with a Dirac gap, it was shown theoretically that [49] valley-polarized output current can be achieved under the modulation of a single nanomagnet.…”

Fully spin-polarized, valley-polarized and spin-valley-polarized electron beam splitters utilizing zero-line modes in a three-terminal device

“…Different types of ZLMs are dependent on different combinations of topological phases between the interfaces, which can be generated by spatially varying external fields. [24][25][26][27] ZLMs containing charge, spin and valley degrees of freedom can simultaneously give rise to abundant charge, spin and valley transport phenomena, which have promising applications in multifunctional devices. [26,28,29] Similar to spintronics, the central issues of valleytronics and spinvalleytronics are the generation and manipulation of valleypolarized and spin-valley-polarized currents, respectively.…”

Valleytronic topological filters in silicene-like inner-edge systems

“…[19] The conductance of the inner-edge states is also robust to various types of longand short-range perturbations. [15,21] It should be noted that kink states, also known as valley inner-edge states, occur in graphene systems [22][23][24][25] or photonic crystals. [26,27] Though the inner-edge states have been extensively investigated, some critical points are still worth exploring in depth.…”

“…[26,27] Though the inner-edge states have been extensively investigated, some critical points are still worth exploring in depth. For example, most inner-edge states focus on the combination of different QVH states, [10,25] QSH and QVH states, [15] or QAH and QVH states. [28] However, other combinations of topological phases are still needed to be investigated.…”