Conducteurs organiques à symétrie contrôlée – 3/4-FILLED

In the framework of this proposal, we suggest the study of new families of molecular conductors. These families are characterized by a ¾ filling of the upper band. A complete study is now possible as the chemistry groups (Rennes and Angers) can control and tune the crystalline structure through hydrogen or halogen interactions. Contrary to the standard ½ filled systems, charge localisation occurs on molecular sites and not on the bonds. As a result, ground states may be modified and it is well known that a ferroelectric charge order (CO) is expected. During the three years, we will establish the phase diagrams and study them deeply through resistivity, dielectric constant, thermopower (Orsay), NMR (Grenoble), ESR (Bordeaux), X-ray diffraction or X-ray diffuse scattering (Orsay). In particular, we expect determining the other ground states which emerge when CO is collapsing after applying hydrostatic pressure or chemical pressure via S/Se substitution. In addition, the introduction of magnetic anions will allow the exploration of systems where ferroelectric and ferromagnetic orders may coexist that is molecular multiferroics.