Perfect valley filter in a topological domain wall

Pan, Hui; Li, Xin; Zhang, Fan; Yang, Shengyuan A.

doi:10.1103/physrevb.92.041404

Cited by 81 publications

(53 citation statements)

References 56 publications

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“…Novel two-dimensional honeycomb lattice materials, such as graphene [9], silicence [10] and transition metal dichalcogenides, [11] host valley degree of freedom. So the manipulation of valley degree of freedom for electrons in these material breeds the new field of valleytronics [12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

The valley filter efficiency of monolayer graphene and bilayer graphene line defect model

et al. 2016

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Figure 3. The performance of model I in the presence of disorder. The results for Anderson (long range) disorder is exhibited in a1-f1 (a2-f2). The other parameters are d=20 and M=100. AbstractIn addition to electron charge and spin, novel materials host another degree of freedom, the valley. For a junction composed of valley filter sandwiched by two normal terminals, we focus on the valley efficiency under disorder with two valley filter models based on monolayer and bilayer graphene. Applying the transfer matrix method, valley resolved transmission coefficients are obtained. We find that: (i) under weak disorder, when the line defect length is over about 15 nm, it functions as a perfect channel (quantized conductance) and valley filter (totally polarized); (ii) in the diffusive regime, combination effects of backscattering and bulk states assisted intervalley transmission enhance the conductance and suppress the valley polarization; (iii) for very long line defect, though the conductance is small, polarization is indifferent to length. Under perpendicular magnetics field, the characters of charge and valley transport are only slightly affected. Finally we discuss the efficiency of transport valley polarized current in a hybrid system.

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Section: Introductionmentioning

confidence: 99%

The valley filter efficiency of monolayer graphene and bilayer graphene line defect model

et al. 2016

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“…Our work provide a promising and effective way to confirm the function of the valley filter. Although our study is based on the BPC valley filter, the idea of detecting valley polarized current by AR can be hopefully extended to other schemes of valley filter [26][27][28][29][30][31][32]. This is reasonable by noting that the electron pairing occurs between ±K valleys, while the valley filter filters one of them.…”

Section: Discussionmentioning

confidence: 99%

Probing the valley filtering effect by Andreev reflection in a zigzag graphene nanoribbon with a ballistic point contact

2017

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Ballistic point contact (BPC) with zigzag edges in graphene is a main candidate of a valley filter, in which the polarization of the valley degree of freedom can be selected by using a local gate voltage. Here, we propose to detect the valley filtering effect by Andreev reflection. Because electrons in the lowest conduction band and the highest valence band of the BPC possess opposite chirality, the inter-band Andreev reflection is strongly suppressed, after multiple scattering and interference. We draw this conclusion by both the scattering matrix analysis and the numerical simulation. The Andreev reflection as a function of the incident energy of electrons and the local gate voltage at the BPC is obtained, by which the parameter region for a perfect valley filter and the direction of valley polarization can be determined. The Andreev reflection exhibits an oscillatory decay with the length of the BPC, indicating a negative correlation to valley polarization.

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“…A DW, a type of topological soliton with a discrete symmetry spontaneously broken, can host intriguing edge states [36,[63][64][65][66][67][68]. Using chirally stacked N-layer graphene supplemented with a gate voltage and a CPL, a DW is designed, as plotted in figure 3(a).…”

Section: Topological Domain Wall and Purely Valley-polarized Chiral Cmentioning

confidence: 99%

Floquet high Chern insulators in periodically driven chirally stacked multilayer graphene

Liu

Yao

2018

New J. Phys.

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Chirally stacked N-layer graphene is a semimetal with ±p N band-touching at two nonequivalent corners in its Brillioun zone. We predict that an off-resonant circularly polarized light (CPL) drives chirally stacked N-layer graphene into a Floquet Chern insulators (FCIs), aka quantum anomalous Hall insulators, with tunable high Chern number C F =±N and large gaps. A topological phase transition between such a FCI and a valley Hall (VH) insulator with high valley Chern number C v =±N induced by a voltage gate can be engineered by the parameters of the CPL and voltage gate. We propose a topological domain wall between the FCI and VH phases, along which perfectly valleypolarized N-channel edge states propagate unidirectionally without backscattering.

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Perfect valley filter in a topological domain wall

Cited by 81 publications

References 56 publications

The valley filter efficiency of monolayer graphene and bilayer graphene line defect model

The valley filter efficiency of monolayer graphene and bilayer graphene line defect model

Probing the valley filtering effect by Andreev reflection in a zigzag graphene nanoribbon with a ballistic point contact

Floquet high Chern insulators in periodically driven chirally stacked multilayer graphene

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