"Moire minibands and Hofstadter fractal spectra
in van der Waals heterostructures of graphene with hexagonal crystals"
Vladimir Falko
Lancaster University
The technological development of graphene has generated new
high-quality systems offer access to the earlier inaccessible extremes
of quantum physics. When graphene is placed on an atomically flat
substrate with hexagonal lattice with a close lattice constant, such
as boron nitride (hBN), and their crystalline axes are aligned, a
long-wavelength perfectly periodic moire pattern forms for electrons
in graphene. In this talk, various regimes of possible moire minibands
at zero magnetic field [Phys. Rev. B 87, 245408 (2013); Phys. Rev. B
88, 205418; Phys. Rev. B 88, 155415 (2013)] and strong magnetic field
[Nature 497, 594 (2013), arXiv:1310.8578] will be discussed.
Experimentally available magnetic fields are enough to provide flux \phi
through the moire superlattice cell comparable to the magnetic flux
quantum \phi0 and reach the regime of fractal Hofstadter spectra. As a
result, a single device can offer a multiplicity of two-dimensional
electron systems, realised at rational flux values \phi= \phi0,
\phi0/2, 2\phi0/3,
etc., each with its own intricate topological properties, including
quantum Hall effect physics related to the effective Landau levels
emerging from these magnetic minibands at the nearby range of magnetic
fields. Several examples of the new minibands emerging from the Dirac
electron spectrum due to the incommensurable or misaligned substrate
offer a way to modify electronic spectrum of graphene.
For more information about the speaker:
http://www.physics.lancs.ac.uk/people/vladimir_falko
Place: SUNUM, Sabanci University
Time: 16 April 2014, 13:40
