報告人 : Leonid Ponomarenko
報告題目 ：Electron Transport in Graphene/BN Superlattices
The superlattice is a regular structure with the period significantly larger than the typical distance between atoms in crystals, but smaller than the electron mean free path. A possibility to control the period and the symmetry of an artificial superlattice makes it an attractive playground for band structure engineering and making conductors with on-demand electronic properties. Recently, high quality two-dimensional superlattices have been obtained by stacking atomically thin materials with similar lattice parameters into heterostructures. The best studied to date are the superlattices of graphene exfoliated on hexagonal boron nitride, on which a range of ground-breaking experiments has been reported including emergence of the secondary Dirac points, observations of the Hofstadter butterfly due to formation of magnetic minibands, the fractal quantum Hall effect and magnetoscillations of conductivity at room temperature.
Behaviour of the two-dimensional superlattice in strong perpendicular magnetic field is of particular interest. In general, B-field must destroy the translation symmetry of any lattice. However, when the magnetic flux through the unit cell becomes the rational fraction of the flux quantum, the translational symmetry is restored and the electron wave function acquires a form of the Bloch wave. This results in the rich behaviour, which includes ballistic transport in strong magnetic fields. In this presentation I will review the electronic properties of superlattices with focus on my own experimental results.