Flat bands and topology in superconductive materials

Ziel

Flat bands allow to increase the critical temperature of the superconducting transition thanks
to their high density of states. However a characterization of the flat bands that support a finite
supercurrent is open. In some cases a nonzero Chern number, a topological invariant of the band
structure, ensures a finite superfluid mass density. This tantalizing relation between topology and
superfluidity is novel and unexplored. My aim is to characterize superfluidity in lattice systems with flat
bands that have different symmetries, lattice structures, dimensionality, interparticle interactions
and possess different topological invariants, in order to provide a general picture of which ones
are potentially useful as a superconductor with high critical temperature. Whereas mean-field (BCS)
theory can provide an essential qualitative understanding and a transparent link to topological properties,
I plan to use more reliable methods such as Density Matrix Renormalization Group (DMRG)
in 1D and Dynamical Mean Field Theory (DMFT) in 2D and 3D. The ideal platform to test the
theoretical predictions are ultracold gases, but I expect to provide useful results also for multiband
superconductors, topological media, carbon-based superconductors, Quantum Hall systems
and high-Tc superconductors.