Pairing and superconductivity in the flat band: Creutz lattice

Rubem Mondaini; G. G. Batrouni; B. Grémaud

doi:10.1103/PhysRevB.98.155142

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Pairing and superconductivity in the flat band: Creutz lattice

Rubem Mondaini, G. G. Batrouni, B. Grémaud

DOI 10.1103/PhysRevB.98.155142 · Physical Review B

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Abstract

We use unbiased numerical methods to study the onset of pair superfluidity in a system that displays flat bands in the noninteracting regime. This is achieved by using a known example of flat band systems, namely, the Creutz lattice, where we investigate the role of local attractive interactions in the U<0 Hubbard model. Going beyond the standard approach used in these systems where weak interactions are considered, we map the superfluid behavior for a wide range of interaction strengths and exhibit a crossover between BCS and tightly bound bosonic fermion pairs. We further contrast these results with a standard two-leg fermionic ladder, showing that the pair correlations, although displaying algebraic decay in both cases, are longer ranged in the Creutz lattice, signifying the robustness of pairing in this system.