SURface MOTT insulators on semiconducting substrates – SURMOTT

The band theory describes successfully a wide variety of materials in the mean-field potential approximation. However, it fails to predict physical properties of strongly correlated systems i.e. Mott insulators. The accurate description of the physics of Mott insulators, especially in low dimension, still poses challenging problems at present. Indeed, the respective role of charge, spin and lattice degrees of freedom of high Tc materials and related systems is still under debate. Semi-conducting surfaces have low coordination surface atoms forming dangling bond-based sp states. These states within surface reconstructions favour electron localization and the formation of Mott phases. Despite their promising qualities, surface Mott insulators and related phases have not been explored in depth so far. This project will study the phase diagram on Sn/Ge and K/Si as a function of fundamental parameters such as bandwith, coulomb repulsion, electron-phonon coupling, temperature and doping. Surface techniques will be applied to tune these parameters and tailor the properties of the systems. A comprehensive study will then be reached by a complete set of experimental techniques (electrons diffraction, scanning probe microscopy, photoemission, high resolution electron energy loss spectroscopy') in association with synchrotron facilities. Band theory ab initio calculations as well as many-body approaches will further support these studies.