Research Seminar – Laurent Bellaiche: Topological Defects in Ferroelectrics and Multiferroics

The seminar flyer can be downloaded here. All welcome.

Abstract:

The use of a first-principles-based effective Hamiltonian in 2004 led to the prediction of a novel structure in zero-dimensional ferroelectrics, in which electric dipoles organize themselves to form a vortex. Such structure exhibits the spontaneous toroidal moment, as its order parameter.

Subsequently, various original phenomena, all related to topological defects, were predicted in ferroelectric and multiferroic nanostructures. Examples include:

(i) the existence of a new order parameter, denoted as the hypertoroidal moment, that is associated with complex dipolar structures (such as double-vortex states);

(ii) the discovery of a new class of quantum materials (denoted as incipient ferrotoroidics), for which zero-point vibrations wash out the vortex state and yield a complex local structure;

(iii) a novel control of magnetism in multiferroic nanodots;

(iv) a shape-induced phase transition involving vortices and antivortices in BaTiO3 platelets; and

(v) the existence of a spontaneous optical activity in systems possessing coupled topological defects.

This seminar will discuss some of these striking phenomena and other recent related developments from our work.

About the speaker:

Distinguished Professor Laurent Bellaiche received his PhD in 1994, from University of Paris VI. He was chosen out of 200 candidates to join the National Renewable Energy Laboratory in 1995 and joined the Department of Physics at the University of Arkansas, as an Assistant Professor in 1999.

Promoted to Distinguished Professor in 2013, Professor Bellaiche’s primary interests are the prediction, design and optimization of properties of semiconductors and ferro electric materials. He uses state-of-the-art band-structure methods to study electronic, structural, optical, dielectric and piezoelectric properties.

His research interests lie in developing and/or using direct first-principles methods, first-principles-based techniques and semi-empirical approaches to calculate properties of ferroelectrics, semiconductors, magnetic compounds and low dimensional systems.

He has co-authored over 275 refereed journal articles, his publications have been cited more than 11,000 times and currently has a h-index of 57. More info on Prof. Bellaiche’ research laboratory, Computational Condensed Matter Physics at the University of Arkansas.