凯发

The talk will review the extremes electronic properties of graphene (G) encapsulated between layers of hexagonal boron nitride (hBN) and device concepts enabled by the high quality of this material. Encapsulation in hBN enables us to achieve a micron-length collision-less propagation of electrons in graphene, whereas technology of making low-resistance edge-contacts with normal and superconducting opens ways to manufacture ballistic electronic devices: electronic lenses and focusing beam splitters, as well as superconducting proximity effect transistors and interferometers. Moreover, electrostatic gating of hBN-G-hBN structures permits to open a large and spatially modulated band gap in bilayer graphene, hence offering new routes towards creating quantum wires, dots, and their various circuits. We shall discuss vertical tunnelling in hBN-G-hBN-G-hBNtunnelling field effect transistors with highly aligned graphene electrodes, where we were able to show resonance tunnelling of ballistic electrons. We shall also discuss extreme physics realised in the highly aligned G-hBN heterostructures, where the long mean free path of carriers enables one to observe the formation of minibands due moiré superlattice determined by the incommensurability of G and hBN crystals, which in strong magnetic field takes the extreme form of a fractal spectrum of Brown-Zak magnetic minibands (also known as Hofstadter’s butterfly).