LAUSR

After the preparation of two-dimensional (2D) electronic flat band (EFB) in van der Waals (vdW) superlattices, recent measurements suggested the existence of one-dimensional (1D) electronic flat bands (1D-EFBs) in twisted vdW bilayers. However, realisation of 1D-EFBs has been experimentally elusive in untwisted 2D layers, which is desired considering their fabrication and scalability. Herein, we report the discovery of 1D-EFBs in an untwisted in situ-grown two atomic-layer Bi(110) superlattice self-aligned on an SnSe(001) substrate using scanning probe microscopy measurements and density functional theory calculations. While the Bi-Bi dimers of Bi zigzag (ZZ) chains are buckled, the epitaxial lattice mismatch between the Bi and SnSe layers induces two 1D buckling reversal regions (BRRs) extending along the ZZ direction in each Bi(110)-11×11 supercell. A series of 1D-EFBs arises spatially following BRRs that isolate electronic states along the armchair (AC) direction and localise electrons in 1D extended states along ZZ due to quantum interference at a topological node. Our work provides a generalised strategy for engineering 1D-EFBs in utilising lattice mismatch between untwisted rectangular vdW layers. This article is protected by copyright. All rights reserved.