Superlight pairs in face-centred-cubic extended Hubbard models with strong Coulomb repulsion

The majority of fulleride superconductors with unusually high transition-temperature to kinetic-energy ratios have a face-centred-cubic (FCC) structure. We demonstrate that, within extended Hubbard models with strong Coulomb repulsion, paired fermions in FCC lattices have qualitatively different properties than pairs in other three-dimensional cubic lattices. Our results show that strongly bound, light, and small pairs can be generated in FCC lattices across a wide range of the parameter space. We estimate that such pairs can Bose condense at high temperatures even if the lattice constant is large (as in the fullerides).

Automated summary

This study demonstrates that paired fermions in face-centred-cubic (FCC) lattices, within extended Hubbard models with strong Coulomb repulsion, have different properties compared to pairs in other three-dimensional cubic lattices. The results show that strongly bound, light, and small pairs can be generated in FCC lattices across a wide parameter space.