Universal behavior of the BCS energy gap Henheik, Sven Joscha ; https://orcid.org/0000-0003-1106-327X Lauritsen, Asbjørn Bækgaard ; https://orcid.org/0000-0003-4476-2288 ddc:500 We consider the BCS energy gap „.T / (essentially given by „.T / .T; p/, the BCS order parameter) at all temperatures 0 T Tc up to the critical one, Tc, and show that, in the limit of weak coupling, the ratio „.T /=Tc is given by a universal function of the relative temperature T =Tc. On the one hand, this recovers a recent result by Langmann and Triola [Phys. Rev. B 108 (2023), no. 10, article no. 104503] on three-dimensional s-wave superconductors for temperatures bounded uniformly away from Tc. On the other hand, our result lifts these restrictions, as we consider arbitrary spatial dimensions d 2 ¹1; 2; 3º, discuss superconductors with non-zero angular momentum (primarily in two dimensions), and treat the perhaps physically most interesting (due to the occurrence of the superconducting phase transition) regime of temperatures close to Tc. ​ . EMS Press 2025 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/19548 https://research-explorer.ista.ac.at/download/19548/19549 Henheik SJ, Lauritsen AB. Universal behavior of the BCS energy gap. <i>Journal of Spectral Theory</i>. 2025;15(1):305–352. doi:<a href="https://doi.org/10.4171/JST/540">10.4171/JST/540</a> eng info:eu-repo/semantics/altIdentifier/doi/10.4171/JST/540 info:eu-repo/semantics/altIdentifier/e-issn/1664-0403 info:eu-repo/semantics/altIdentifier/wos/001438931600009 info:eu-repo/semantics/altIdentifier/arxiv/2312.11310 https://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess