Shear-induced electronic confinement and one-dimensional bands in two-dimensional undulated bilayer semiconductors

Two-dimensional (2D) materials can significantly change their properties in response to external influences, such as stacking orientation or in-plane strain, forming materials with novel electronic structures. In this poster, I will show the emergence of an effective one-dimensional (1D) system (similar to quantum wells) using a periodic one-dimensional bending modulation of a 2D semiconductor bilayer without in-plane strain. The appearance of 1D electronic bands arising due to the confinement along the modulated direction is illustrated by a two-ladder one-dimensional tight binding (TB) model and also confirmed by density functional theory (DFT) calculations using undulated bilayer hexagonal boron nitride (hBN) as an example. The bending modulation of a 2D bilayer creates an interlayer shear gradient, which creates moiré patterns with different stackings along the modulated direction. The changing stacking pattern creates a long-range electrostatic confinement potential, resulting in 1D electronic flat bands. The obtained 1D states are very similar in property to the widely studied 1D quantum wells in bulk semiconductors and demonstrate that shear gradients generated by undulating 2D bilayers can be used as a novel way to create 1D quantum wells in 2D materials. Additionally, the 1D states of undulated 2D bilayers can significantly affect photogenerated carriers' lifetime and increase optoelectronic devices' performance.