Enhanced robustness of zero-line modes in graphene via magnetic field

Abstract

Motivated by recent experimental results for zero-line modes (ZLMs) in a bilayer graphene system [Nature Nanotechnol. 11, 1060], we systematically studied the influence of a magnetic field on ZLMs and demonstrated the physical origin of the enhanced robustness by employing nonequilibrium Green's functions and the Landauer-Büttiker formula. We found that a perpendicular magnetic field can separate the wavefunctions of the counter-propagating kink states into opposite directions. Specifically, the separation vanishes at the charge neutrality point. The separation increases as the Fermi level deviates from the charge neutrality point and can reach a magnitude comparable to the wavefunction spread at a moderate field strength. Such spatial separation of oppositely propagating ZLMs effectively suppresses backscattering. Moreover, the presence of a magnetic field enlarges the bulk gap and suppresses the bound states, thereby further reducing the scattering. These mechanisms effectively increase the mean free paths of the ZLMs to approximately 1 µm in the presence of a disorder.

Gate controlled valley polarizer in bilayer graphene

“…Instead, gate-controlled chiral channels could provide a robust and flexible approach for valleytronic operations. Theory predicted that 10,[16][17][18] sign reversal of Berry curvature in adjacent regions in bilayer graphene (BLG) offers a scheme to produce topological valley-polarized one-dimensional (1D) channels. This can be achieved by dual-split gates (Fig.…”

“…Good contrast between even and odd-field configuration was achieved only in the presence of an external magnetic field 1 . The external magnetic field helps 18 to spatially separate the counter-propagating channels and hence suppress backscattering. At high magnetic field of 8 T, the work demonstrated nearly ballistic transport confirmed by the observation of four quantized conductance channels in the odd-field configuration.…”

Hidden Wave Function of Twisted Bilayer Graphene: Flat Band as a Landau Level

“…Introduction. Twisted bilayer graphene (TBG) has recently drawn a lot of attention from the physics community due to its interesting properties and applications [1] - [40]. One of the most prominent features is the recent discovery of correlated insulators and superconductivity, that are observed in a narrow range of twist angles near θ = 1.05 • , which is usually referred to as the magic angle.…”

Metallic Network of Topological Domain Walls

“…Although these zero lines have been experimentally realized in gated bilayer graphene through precisely aligned dual gated devices [20][21][22], it is technologically very challenging to devise a periodic network of intersecting topological domain walls using similar techniques [8]. Fortunately, recent experiments on twisted layered van der Waals materials pave a natural pathway to explore ZLMs networks [23][24][25][26][27][28][29][30][31][32][33][34][35]. The most representative system is the twisted bilayer graphene, where a moiré pattern forms to arrange the AB/BA stacking domains periodically in space [23][24][25][26][27][28][29][30][31][32].…”

“…Fortunately, recent experiments on twisted layered van der Waals materials pave a natural pathway to explore ZLMs networks [23][24][25][26][27][28][29][30][31][32][33][34][35]. The most representative system is the twisted bilayer graphene, where a moiré pattern forms to arrange the AB/BA stacking domains periodically in space [23][24][25][26][27][28][29][30][31][32]. When a perpendicular electric field is applied via electric gating or built-in electric fields from substrates, those chiral stacking domains become insulating with a finite valley Chern number, and give rise to a network of conducting domain wall ZLMs [6,[10][11][12][13][14][15][16].…”