Theory of Slidetronics in Ferroelectric van der Waals Layers

TL;DR

This paper develops a symmetry-based theory of slidetronics in 2D ferroelectric layers, showing how interlayer sliding can switch polarization states and guiding the design of materials with tailored polarization properties.

Contribution

It introduces a symmetry principle framework for classifying and understanding polarization switching via interlayer sliding in 2D ferroelectric materials, including multilayer configurations.

Findings

Sliding-induced polarization inversion is impossible in bilayers.

Multilayers like PdSe2 trilayers can achieve polarization switching.

The theory guides the design of 2D ferroelectrics with specific switching behaviors.

Abstract

Vertically stacked layers derived from non-ferroelectric monolayers offer a promising route to two-dimensional (2D) ferroelectrics, where polarization switching occurs via interlayer sliding at sub-unit cell scales. Here, we develop a theory of slidetronics based on the notion that sliding-induced switching $P \rightarrow P'$ can also be achieved by applying an appropriate point-group operator $G$ to the entire system, such that $P' = G P$. Interlayer sliding and the transformation induced by the generator $G$ are thus equivalent in describing the relationship between the initial and final layer configurations. From this symmetry principle, we deduce that slidetronics can be classified by generators $G$; the generator $G$ must act as a symmetry operator for the constituent layers, while it is not a symmetry operator for the stacked layers as a whole; for a given 2D material, $G$ determines the interlayer sliding required for polarization switching; and sliding-induced complete polarization inversion is impossible in bilayers but can be realized in multilayers (e.g., PdSe$_2$ trilayers). These findings provide a framework for designing 2D ferroelectrics with targeted polarization-switching properties, as demonstrated through case studies of real materials.