Contrôle des propriétés électroniques des matériaux quasi-2D sous contraintes biaxiales

As part of the ongoing search for new material properties that could present fundamental and application interest, efforts are constantly being made to create new materials and study them under new experimental conditions. To do so, phase diagrams need to be studied as exhaustively as possible. Several parameters are commonly modified to access the physical parameters of materials: temperature, pressure, magnetic and electric fields, doping or chemical substitution, etc. In this work, we will follow a new, original and promising route to access the new electronic properties of crystalline materials, by carrying out biaxial deformation at cryogenic and at room temperature, and by going beyond current achievements in this field. Indeed, the electronic properties are intimately linked to the atomic structure of crystals, and any deviation from this can lead to radically different properties, such as a shift in phase transition temperatures, or even lead to new atomic or electronic phases. We will apply this methodology to materials with electronic vacancies, as they exhibit fantastic and diverse electronic properties relevant to applications: semiconductors, superconductors and metal-insulator systems in general. More specifically, we will study new phases in quasi-2D systems, the RTe3 (R = rare earth) which already exhibit charge density waves (CDW) and superconductivity (SC) in the (T,P) phase diagram, and we will study the evolution of transition temperatures as a function of biaxial tensile stress. To this end, a biaxial stress device operating at low temperature and compatible with X-ray diffraction, in-situ transport measurements and optical measurements has been developed at the Laboratoire de Physique des Solides. Initially, this new device will be assembled and characterised, and initial biaxial deformation tests will be carried out, following the deformation of samples by X-ray diffraction. Next, the deformations will be induced in the samples, where the structural parameters will be measured, as well as the parameters related to CDW such as the transition temperature. Finally, changes in resistivity will be followed using in-situ transport measurements to obtain information on changes related to the geometry of the Fermi surface.