Ferroelectricity in 2D materials: the CNR and Unimore study

The central element of the discovery lies in identifying the causes that guarantee the stability of the two states of opposite polarization, an essential condition for being able to encode digital information in the form of binary bits. The analysis conducted by the researchers highlights that the confinement of electrons in a two-dimensional geometry amplifies mutual quantum interactions, inducing the particles to move in a collective and coordinated way. This electronic cooperation generates a higher energy barrier, which protects the stability of the polarization and makes it robust against external perturbations. Matteo D’Alessio, PhD student in Physics and Nanosciences at Unimore, specified the importance of the phenomenon: “IIn these systems the electrical polarization depends on how the electrons are distributed between the layers and can be reversed by making one atomic layer slide slightly relative to the other. This property potentially paves the way for faster and more efficient devices, but it is essential to understand and control the stability of the two states with opposite polarization and the process that leads from one to the other”.

From a methodological point of view, the scientific investigation integrated the use of advanced numerical simulations based on calculations from first principles, i.e. predictive physical models that do not use empirical parameters but are based exclusively on the fundamental laws of quantum mechanics. The development of these theoretical architectures required the use of high-performance computing infrastructures, capable of processing large amounts of structural data.

Massimo Rontani, Cnr-Nano researcher, clarified the novelty of the model: “When electrons are confined in two dimensions, they influence each other and tend to behave collectively, coordinating their motion. This behavior makes the electrical polarization more robust by increasing the energy barrier that protects it. This is a mechanism not yet considered in theoretical models, which helps to better understand ferroelectricity in these new materials with high application potential”.

The research activities are part of the programmes study on quantum materials supported by the European Center of Excellence MaX and by ICSC, the National Research Center in High Performance Computing, Big Data and Quantum Computingoutlining a prospect of transferability of these models to a broad class of two-dimensional semiconductors for next-generation integrated circuits.

Cover image: Schematic of the two-dimensional WTe₂ (tungsten ditelluride) material and the flow process between the layers. The graphs show the energy barrier associated with polarization: higher when the collective quantum behavior of electrons is taken into account, lower if this effect is not taken into account.