Gate-tunable current partition in graphene-based topological zero lines

Wang, Ke; Ren, Yafei; Deng, Xinzhou; Yang, Shengyuan A.; Jung, Jeil; Qiao, Zhenhua

doi:10.1103/physrevb.95.245420

Cited by 27 publications

(19 citation statements)

References 34 publications

(35 reference statements)

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“…Therefore, the ratio γ ≡ P ab /P ac can deviate from 1. Microscopically, the magnetic field shifts the domain-wall states away from the zero-field positions [34][35][36], and the junction is subsequently modified [37]. We first consider the case where the B field is small and γ can be approximated by its zero-magnetic-field value (i.e., γ = 1).…”

Section: Hofstadter Butterfly and Dirac Pointsmentioning

confidence: 99%

Hofstadter butterfly and Floquet topological insulators in minimally twisted bilayer graphene

Chou

Sarma

2020

Phys. Rev. Research

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We theoretically study the Hofstadter butterfly of a triangular network model in minimally twisted bilayer graphene. The band structure manifests periodicity in energy, mimicking that of Floquet systems. The butterfly diagrams provide fingerprints of the model parameters and reveal the hidden band topology. In a strong magnetic field, we establish that minimally twisted bilayer graphene realizes low-energy Floquet topological insulators (FTIs) carrying zero Chern number, while hosting chiral edge states in bulk gaps. We identify the FTIs by analyzing the nontrivial spectral flow in the Hofstadter butterfly, and by explicitly computing the chiral edge states. Our theory paves the way for an effective practical realization of FTIs in equilibrium solid-state systems.

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Section: Hofstadter Butterfly and Dirac Pointsmentioning

confidence: 99%

Hofstadter butterfly and Floquet topological insulators in minimally twisted bilayer graphene

Chou

Sarma

2020

Phys. Rev. Research

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“…25 suggests the observed conductance cannot be attributed to the quantum Hall effect. In addition to enhancing the robustness of the topological chiral channels, the magnetic field provides an external parameter that controls the microscopic properties of the electron modes 21,30 . In particular, we focus on the asymmetric lateral and layer distribution 24 of the electronic wavefunctions due to explicit symmetry breaking by the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Effects on Topological Chiral Channels in Bilayer Graphene

Winn¹,

Maier²,

Jiao³

et al. 2019

Preprint

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We study the effect of a magnetic field on topological chiral channels of bilayer graphene at electric domain walls. The persistence of chiral edge states is attributed to the difference in valley Chern number in the regions of opposite electric field. We explore the regime of large electric and magnetic fields perpendicular to the lattice. The magnetic field shifts the channel away from our electric interface in a way that is inconsistent with the semiclassical expectation from the Lorentz force. Moreover, the magnetic field causes an imbalanced layer occupation preference to the chiral channels. These behaviors admit analytic solutions in the limits that either the electric or the magnetic field dominates. We numerically show in the general case that the system can be wellapproximated as a weighted sum of the two limits.

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“…At the intersection between zero lines of quantum valley Hall effect, counterintuitive current partition was reported [36], and later the tunable current partition at multiple intersections was also demonstrated [37]. In these systems, time-reversal invariance guarantees the helical transport of these ZLMs.…”

mentioning

confidence: 99%

Tunable current partition at zero-line intersection of quantum anomalous Hall topologies

et al. 2017

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At the interface between two-dimensional materials with different topologies, topologically protected one-dimensional states (also named as zero-line modes) arise. Here, we focus on the quantum anomalous Hall effect based zero-line modes formed at the interface between regimes with different Chern numbers. We find that, these zero-line modes are chiral and unilaterally conductive due to the breaking of time-reversal invariance. For a beam splitter consisting of two intersecting zero lines, the chirality ensures that current can only be injected from two of the four terminals. Our numerical results further show that, in the absence of contact resistance, the (anti-)clockwise partitions of currents from these two terminals are the same owing to the current conservation, which effectively simplifies the partition laws. We find that the partition is robust against relative shift of Fermi energy, but can be effectively adjusted by tuning the relative magnetization strengths at different regimes or relative angles between zero lines. PACS numbers:Introduction-. The presence of edge states that are topologically protected from backscattering is one of the striking hall-marks of topologically nontrivial insulators [1][2][3][4][5]. According to the rigorous bulk-edge correspondence rule [6,7], edge states appear at the boundary of two-dimensional topological systems, like quantum Hall effect [8], quantum anomalous Hall effect [9,10], and quantum spin-Hall effect (or two-dimensional topological insulators) [11,12]. These edge states are localized at the boundaries that are interfaces between topological materials and topologically trivial vacuum. Thus, these boundaries can be generalized to interfaces between two topologically distinct materials, like the interface between quantum anomalous Hall effect and quantum valley Hall effect [13], quantum spin-Hall effect and quantum valley Hall effect [14], or the graphene nanoroad between two structurally different boron-nitride sheets [15]. One widely explored system is the zero-line modes (ZLMs) occurred at the interface, across which the valley Chern numbers varies [1,16]. These ZLMs are protected from long-range scattering potential by large momentum separation and exhibit zero bend resistance in the absence of atomic defects [15,17]. Such modes are experimentally feasible [19,20] in Bernal stacked multilayer graphenes with out-of-plane electric field [21][22][23] and have attracted much attention from both theoreticians [1,17,18,[24][25][26][27][28][29][30][31][32][33][34] and experimentalists [19,20,35].

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Gate-tunable current partition in graphene-based topological zero lines

Cited by 27 publications

References 34 publications

Hofstadter butterfly and Floquet topological insulators in minimally twisted bilayer graphene

Hofstadter butterfly and Floquet topological insulators in minimally twisted bilayer graphene

Magnetic Effects on Topological Chiral Channels in Bilayer Graphene

Tunable current partition at zero-line intersection of quantum anomalous Hall topologies

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