Valley polarization assisted spin polarization in two dimensions

International audienceValleytronics is rapidly emerging as an exciting area of basic and applied research. In two dimensional systems, valley polarisation can dramatically modify physical properties through electron-electron interactions as demonstrated by such phenomena as the fractional quantum Hall effect and the metal-insulator transition. Here, we address the electrons' spin alignment in a magnetic field in silicon-on-insulator quantum wells under valley polarisation. In stark contrast to expectations from a non-interacting model, we show experimentally that less magnetic field can be required to fully spin polarise a valley-polarised system than a valley-degenerate one. Furthermore, we show that these observations are quantitatively described by parameter free ab initio quantum Monte Carlo simulations. We interpret the results as a manifestation of the greater stability of the spin and valley degenerate system against ferromagnetic instability and Wigner crystalisation which in turn suggests the existence of a new strongly correlated electron liquid at low electron densities

Back-end-of-line compatible conductive bridging RAM based on Cu and SiO2

International audienc

Back-end-of-line compatible conductive bridging RAM based on Cu and SiO2

International audienc

Z (nm)

International audienceWe report on the fabrication of a clean, stable in room atmosphere and superconducting surface consisting of graphene on tantalum carbide (TaC) obtained by high-temperature annealing of a tantalum thin film on SiC. Low temperature scanning tunneling spectroscopy reveals that the surface is superconducting with a superconducting order parameter up to 1.6 meV. In addition, atomically-resolved imaging establishes the chemical inertness of the surface. This result is achieved because few graphene layers protect the surface superconductivity of the buried superconducting TaC formed during the high-temperature annealing