@article{22290,
  abstract     = {We introduce a multi-band BCS free energy functional and prove that for a multi-band superconductor the effect of inter-band coupling can only increase the critical temperature, irrespective of its attractive or repulsive nature and its strength. Further, for weak coupling and weaker inter-band coupling, we prove that the dependence of the increase in critical temperature on the inter-band coupling is (1) linear, if there are two or more equally strongly superconducting bands, or (2) quadratic, if there is only one dominating band.},
  author       = {Henheik, Sven Joscha and Langmann, Edwin and Lauritsen, Asbjørn Bækgaard},
  issn         = {1424-0661},
  journal      = {Annales Henri Poincaré},
  publisher    = {Springer Nature},
  title        = {{Multi-band superconductors have enhanced critical temperatures}},
  doi          = {10.1007/s00023-026-01706-y},
  year         = {2026},
}