Emergent Electronic Insulating States in a One-Dimensional Moiré Superlattice.

Two-dimensional van der Waals (vdW) moiré superlattices have provided a powerful knob to engineer a plethora of new quantum states. However, extending such moiré engineering to one-dimensional (1D) vdW systems has remained challenging. Here, we report the creation of moiré-engineered electronic insulating states in a new 1D moiré superlattice by crystallographically aligning an armchair single-walled carbon nanotube (SWNT) to a two-dimensional hexagonal boron nitride (hBN) substrate. Remarkably, we observe the emergence of pronounced insulating states at the charge neutrality point and at full and half moiré fillings in lattice-aligned armchair SWNT/hBN heterostructures using low-temperature electrical transport measurements. In strong contrast, armchair SWNT devices without hBN alignment do not show any of these insulating behaviors, which provides compelling evidence of a significant 1D moiré effect. Our density functional theory and tight-binding calculations reveal that synergetic nanotube partial flattening and in-plane lattice reconstruction at the 1D moiré interface expand the most stable AB' stacking regions (carbon on top of boron) and open sizable band gaps at both the charge neutrality point and full moiré fillings at the single-particle level. Our one-body theory predicts no band gaps at half moiré fillings, suggesting that electron correlation and/or Peierls distortion may give rise to these emergent insulating behaviors in our 1D moiré systems. Our Letter establishes a new and definite moiré engineering route for 1D vdW materials and opens an exciting avenue for exploring interaction-driven quantum phases in 1D.