Magnetism and superconductivity under extreme conditions by x-ray techniques

Abstract

In this project we propose to study the competition between magnetism and superconductivity and its dependence on electron density and correlation in high electron density systems and as a function of external pressure applied to induce high atomic and electron density. In order to do this, we will explore two classes of materials: heavy fermion intermetallics, which exhibit unconventional superconductivity with coexistence of low temperature magnetism, and hydrogen based compounds that are or are expected to exhibit high temperature superconductivity at high pressures. For this purpose, we will use x-ray spectroscopic techniques (XAS / XMCD), XRD and macroscopic measurements of magnetic susceptibility and electrical resistivity, all under extreme conditions of pressure and temperature. In the case of heavy fermion compounds (eg CeMIn5, M=Co, Rh and Ir) we will study the competition between magnetism and superconductivity in terms of changes in electronic and magnetic structures due to high pressures, including behaviors close to the quantum critical point. For hydrogen-based compounds, high-temperature superconducting states will be sought under extremely high pressure conditions. The parallel between these two classes of materials under these conditions can provide a broad view on the appearance of superconducting phases at high density and changes in the electronic structure induced by pressure, which may contribute to a global understanding of the phenomenon of superconductivity and its relations with electronic and magnetic properties of a great diversity of compounds.