RhomboG

This project aims at the elaboration and fabrication of thin layers of graphite (nanometer thickness, 10-30 layers) with a rhombohedral stacking. This carbon polytype is not the most stable in ambient conditions and is hence much less abundant than the well-known Bernal stacked polytype. Electronic properties of this material are unknown for specimens composed of more than 3 layers. We have developed techniques allowing for either the direct growth of this material on a 3C-SiC substrate, or for the identification of rhombohedral inclusions within bulk graphite. Similar to cristaline topological insulators, this material is expected to host surface electronic states with flat electronic dispersions and hence, an important density of states which favors the emergence of exotic electronic ground state such as magnetism or superconductivity. This material represents a unique type of electronic system in condensed matter physics. We will produce different types of structures of rhombohedral graphite flakes on substrates adapted for a wide range of investigations. In particular, we will investigate the band structure of this new material with tunneling spectroscopy, ARPES, as well as magneto-transport and low energy magneto-Raman scattering. We aim at investigating low energy electronic excitations of electrons in flat bands to characterize the electronic ground state of rhombohedral thin graphite layers for identified structures of various thicknesses, to trace the evolution of the band structure as a function of number of layers. Ab-initio calculations will guide our experimental work on phonon and electronic properties, as well as on the possible electronic instabilities affecting the highly degenerated electronic state within the flat band. We will fabricate prototypes of elementary components (FET and lateral spin valve) to investigate the potential of this material for applications in microelectronics and in spintronics.