Merons and antimerons

Merons and antimerons - 28/03/2023

Sliding and twisting of van der Waals layers can produce fascinating physical phenomena. In a recent publication we show that moiré polar domains in bilayer hBN give rise to a topologically non-trivial winding of the polarization field, forming networks of merons and antimerons.

Polar meron-antimeron networks in strained and twisted bilayers. D. Bennett, G. Chaudhary, R.J. Slager, E. Bousquet and Ph. Ghosez, Nature Communications 14, 1629 (2023).

Modeling of ferroelectric oxide perovskites : from first to second principles.

Modeling of ferroelectric oxide perovskites : from first to second principles. - 28/07/2022

Taking a historical perspective, we provide a brief overview of the first-principles modeling of ferroelectric perovskite oxides over the past 30 years. We emphasize how the work done by a relatively small community on the fundamental understanding of ferroelectricity and related phenomena has been at the origin of consecutive theoretical breakthroughs, with an impact going often well beyond the limit of the ferroelectric community. In this context, we first review key theoretical advances such as the modern theory of polarization, the computation of functional properties as energy derivatives, the explicit treatment of finite fields, or the advent of second-principles methods to extend the length and timescale of the simulations. We then discuss how these have revolutionized our understanding of ferroelectricity and related phenomena in this technologically important class of compounds.

The simplest multiferroic

The simplest multiferroic - 14/11/2020

Motivated by the seminal theoretical prediction of strain-induced ferroelectricity in binary oxides done in 2010 [E. Bousquet, N. A. Spaldin & Ph. Ghosez, Phys. Rev. Lett. 104, 037601 (2010)],the possible appearance of ferroelectricity in ferromagnetic EuO under epitaxial strain has been investigated in thin films and superlattices. Achieving compressive epitaxial strains up to more than 6%, the study confirms the original theoretical prediction, making strained EuO the simplest known multiferroic material. 

Making EuO multiferroic by epitaxial strain engineering, V. Gian, R. Held, E. Bousquet, Y. Yuan, A. Melville, H. Zhou, V. Gopalan, Ph. Ghosez, N. A. Spaldin, D. G. Schlom & S. Kamba, Communications Materials 1, 74 (2020).