Revisiting flat band superconductivity: Dependence on minimal quantum metric and band touchings

A central result in superconductivity is that flat bands, though dispersionless, can still host a nonzero superfluid weight due to quantum geometry. In this article, Kukka-Emilia Huhtinen, Jonah Herzog-Arbeitman, Aaron Chew, Bogdan A. Bernevig, and Päivi Törmä show that the derivation of the mean field superfluid weight in previous literature is incomplete, which can lead to severe quantitative and even qualitative errors. They derive the complete equations and demonstrate that the minimal quantum metric, the metric with minimum trace, is related to the superfluid weight in isolated flat bands. They complement this result with an exact calculation of the Cooper pair mass in attractive Hubbard models with the uniform pairing condition.

Read the whole article in Physical Review B.