Topological Valley Transport in Bilayer Graphene Induced by Interlayer Sliding

Abstract

Interlayer sliding, together with twist angle, is a crucial parameter that defines the atomic registry and thus determines the properties of two-dimensional (2D) material homobilayers. Here, we theoretically demonstrate that controlled interlayer sliding in bilayer graphene induces Berry curvature reversals, leading to topological states confined within a one-dimensional moiré channel. We experimentally realize interlayer sliding by bending the bilayer graphene geometry across a nanoridge. Systematic electronic transport measurements reveal topological valley transport when the Fermi energy resides within the band gap, consistent with theoretical predictions of eight topological channels. Our findings establish interlayer sliding as a powerful tool for tuning the electronic properties of bilayer graphene and underscore its potential for broad application across 2D material systems.

Figures (4)

• Figure 1: Bilayer graphene with interlayer sliding. Schematic illustration of bilayer graphene lattice structure with interlayer sliding along armchair direction, with sliding distance varying from 0 to $a$. To open a band gap, we assign a weak layer-dependent potential difference, $V = \pm 0.02t$, where $t$ is the nearest-neighbor intralayer hopping strength. Bandstructure of bilayer graphene with interlayer sliding is exhibited by black curves in the lower panel with color red(blue) denotes the positive(negative) Berry curvature.
• Figure 2: Bilayer graphene on nano-ridge. (a) Schematic illustration of experimental method for generating interlayer sliding in AB stacking bilayer graphene, forming AA$^\prime$ and BA stacking on right side, and AA/AB stacking on left side of the nano-ridge. (b) Bandstructure of bilayer graphene with interlayer sliding. Gray curves correspond to bulk states of AB or BA stacking and four red/blue curves represent topological state at AA$^\prime$ moiré channel from K/K$^\prime$ valley.
• Figure 3: 4-probe measurement results of bilayer graphene with interlayer sliding. Schematic illustrations of (a) experimental setup of heterostructures h-BN/bilayer graphene/h-BN/few-layer graphene and (b) 4-probe measurements. At $T=2$ K, 4-probe resistance for different bottom and top gate voltages is summarized in (c) with enlarged view in (d). (e) For fixed $T=2$ K, 4-probe resistance as a function of carrier density for different displacement fields. (f) Measured $V_{\rm dip}$ as a function of displacement field. 4-probe resistance as a function of carrier density for fixed displacement field $|D| =0.7$ V/nm under different temperatures are shown in (g) with enlarged view in (h). The inset demonstrates the positive correlation between critical temperature and displacement field.
• Figure 4: Source-drain resistance of bilayer graphene with interlayer sliding. (a) Source-drain resistance as a function of back gate voltage for different displacement fields. (b) Open squares denote saturated conductance for different channel length $L$ of five samples and red curve represents fittings of Landauer-Büttiker formula with $L_{\rm mfp} = 1$${\rm \mu}$m.