title: Geometric Origin of Superfluidity in the Lieb-Lattice Flat Band.
abstract: The ground state and transport properties of the Lieb lattice flat band in the presence of an attractive Hubbard interaction are considered. It is shown that the superfluid weight can be large even for an isolated and strictly flat band. Moreover the superfluid weight is proportional to the interaction strength and to the quantum metric, a band structure quantity derived solely from the flat-band Bloch functions. These predictions are amenable to verification with ultracold gases and may explain the anomalous behavior of the superfluid weight of high-T_{c} superconductors.
authors: COMP Centre of Excellence, Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland.
authors: Aleksi
authors: A
authors: Julku
authors: COMP Centre of Excellence, Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland.
authors: Sebastiano
authors: S
authors: Peotta
authors: COMP Centre of Excellence, Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland.
authors: Tuomas I
authors: TI
authors: Vanhala
authors: Department of Physics and Photon Science, School of Physics and Chemistry, Gwangju Institute of Science and Technology, Gwangju 61005, Korea.
authors: Dong-Hee
authors: DH
authors: Kim
authors: COMP Centre of Excellence, Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland.
authors: Päivi
authors: P
authors: Törmä