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Title: Superconducting transitions in flat-band systems

The physics of strongly correlated quantum particles within a flat band was originally explored as a route to itinerant ferromagnetism and, indeed, a celebrated theorem by Lieb rigorously establishes that the ground state of the repulsive Hubbard model on a bipartite lattice with unequal number of sites in each sublattice must have nonzero spin S at half-filling. Recently, there has been interest in Lieb geometries due to the possibility of novel topological insulator, nematic, and Bose-Einstein condensed (BEC) phases. In this paper, we extend the understanding of the attractive Hubbard model on the Lieb lattice by using Determinant Quantum Monte Carlo to study real space charge and pair correlation functions not addressed by the Lieb theorems. Specifically, our results show unusual charge and charge transfer signatures within the flat band, and a reduction in pairing order at ρ = 2/3 and ρ = 4/3, the points at which the flat band is first occupied and then completely filled. Lastly, we compare our results to the case of flat bands in the Kagome lattice and demonstrate that the behavior observed in the two cases is rather different.
 [1] ;  [2] ;  [3] ;  [4] ;  [1]
  1. Univ. of California, Davis, CA (United States). Physics Dept.
  2. Univ. of Nice Sophia Antipolis (France)
  3. CNRS-UNS-NUS-NTU International Joint Research Unit (Singapore); Ecole Normale Superieure, Paris (France). Kastler Brossel Lab.; National Univ. of Singapore (Singapore). Centre for Quantum Technologies and Dept. of Physics
  4. Univ. of Nice Sophia Antipolis (France); National Univ. of Singapore (Singapore). Centre for Quantum Technologies; Inst. Univ. of France, Paris (France)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
NA0001842; NNSA-DE-NA0001842-0
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 90; Journal Issue: 9; Journal ID: ISSN 1098-0121
American Physical Society (APS)
Research Org:
Univ. of California, Davis, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States