Superconductivity in flat bands in the square-otagon lattice
Lattice square-octagon; Flat band; Superconductivity;
The superconducting state in conventional superconductors is achieved when a metal is subjected to temperatures near absolute zero. However, obtaining such low temperatures requires sophisticated techniques, making some applications impractical. In this work, conditions for the emergence of flat bands in the square-octagon lattice were investigated. As a result, four bands were identified, with two being dispersive and two being flat. Interestingly, one dispersive band is sandwiched between two flat bands. The other dispersive band found is isolated from the remaining bands. However, this latter band
does not contribute to the formation of the superconducting state. Therefore, a model featuring a dispersive band sandwiched between two flat bands was considered. Finally, an attractive interaction was introduced, leading to the self-consistent equation for the critical temperature, resulting in a superconducting phase diagram resembling those measured for unconventional superconductors