Multiple orders in correlated fermions materials

Principal interests

Our team works on materials presenting remarkable properties due to the interaction between electrons. These electronic interactions strongly depend on the nuclear and/or magnetic structure of theses materials and reciprocally affect it. This strong structure-properties interdependence is at the heart of the so called strongly correlated material which is the center of our research activity. We focus on a small amount of properties where X-rays (in our laboratory or in Synchrotron) and neutron (Large Facilities) scattering are the most relevant tools to elucidate.

Members

Research thematics

Multiferroicity is defined as the concomitant presence of several orders such as magnetism, ferroelectricity … in the same range of the phase diagramm (pressure, temperature). What make them interesting is the coupling between these orders, with the potential control of the magnetism through an external electric field. This is the case for RMn₂O₅ family of compounds (R=rare earth) we are studying. Implications of the understanding of this coupling may find technological development in the spintronic or magnetic storage device domains.

High temperature superconductivity present a very peculiar interaction between electron : it is actually attractive. However the microscopic mechanism for such pairing is still to be found. We recently revealed the link betwen nuclear structure and electronic structure in the famous iron base superconductor BaFe₂As₂. We thus identify a key parameter responsible for the appearance of supeconductivity in this compound.

Mott insulators are material presenting a metal to insulator transition as a funciton of external parameters such as pressure or temperature. VO₂ or V₂O₃ are the archetypical materials. Without electronic interaction – in the Fermi liquid theory framework -, they are expected to be metallic. However the repulsion is so strong that it localize the electrons, resulting in an insulator state. We study these phases transitions in various systems, from these Vanadium oxydes to organic conductors or superconductors.