Speaker
Dr
Wolfgang Häusler
(University of Augsburg, Germany)
Description
Abstract: Dispersionless (“flat”) electronic bands can arise
throughout the Brillouin zone in certain multipartite lattices,
besides ordinary dispersing bands. In such a flat band,
hoppings between atomic orbitals interfere destructively
which then leads to localization, a phenomenon denoted as
“caging” of carriers. As a consequence, the system is
insulating at zero temperature even when this band is
partly filled, provided all other bands are either empty or
completely filled. One may ask whether long range Coulomb
interactions can alter this situation and cause finite
conductivity. In the absence of kinetic energy, flat band
carriers tend to Wigner crystallize. Here, this general
observation is analyzed for the two-dimensional case
specifically for the Sutherland or T3 –lattice where a
conductivity is found, depending non-trivially on the carrier
density at small flat band fillings.
