James BOUST

Post-doc

Resarch activities at CPHT: Condensed Matter

Thesis: "First-principles theory of magnetic intermetallics"
Advisor: Leonid Pourovskii
PhD defense on november 18, 2022 at Ecole Polytechnique.

Abstract : In so-called "strongly correlated" materials, the strong Coulomb interaction which correlates the movement of electrons at the atomic scale can give rise to outstanding properties at the macroscopic scale. The materials studied in this thesis contain rare-earth elements (like neodymium) which usually exhibit these strong correlation effects. Due to their remarkable properties, rare-earth compounds have numerous technological applications; they are for instance used as high-performance magnets in electric motors. The demand for rare earths is therefore increasing; on the other hand, mining them is difficult, expensive and polluting. Hence, optimizing the properties and composition of rare-earth-based materials can be of great technological, economical and environmental interest. From the point of view of theoretical physics, describing these materials constitutes a real challenge, precisely due to their strongly correlated nature. In this thesis, we develop theoretical approaches to study the magnetic and optical properties of rare-earth compounds, notably the industrially relevant neodymium magnet. These theoretical methods are said to be from "first principles" as they are based on the fundamental laws governing the physics at the atomic level.

Publications :

Boust J, Galler A, Biermann S, Pourovskii L.
Combining semilocal exchange with dynamical mean-field theory: Electronic structure and optical response of rare-earth sesquioxides.
Physical Review B. 2022;105(8):085133.
DOI: 10.1103/PhysRevB.105.085133.

Galler A, Boust J, Demourgues A, Biermann S, Pourovskii LV.
Correlated electronic structure and optical response of rare-earth based semiconductors.
Physical Review B. 2021;103(24):L241105.
DOI: 10.1103/PhysRevB.103.L241105.

Pourovskii LV, Boust J, Ballou R, Eslava GG, Givord D.
Higher-order crystal field and rare-earth magnetism in rare-earth-Co5 intermetallics.
Physical Review B. 2020;101(21):214433.
DOI: 10.1103/PhysRevB.101.214433.