Superconducting length scales from microscopic theories

by Niklas Witt

Thursday Jul 9, 2026, 2:15 PM → 3:45 PM Europe/Berlin

D5-153 (UHG)

Theoretical descriptions of superconductors have become increasingly quantitative, but are still often focused on superconducting instabilities rather than the full set of experimentally relevant properties. Among these are the superconducting coherence length and penetration depth, which govern critical fields, currents, and electromagnetic response. Despite their central role to superconducting functionality, these quantities are rarely accessed in microscopic studies, particularly in strongly correlated materials. In this talk, I present a general framework to compute superconducting length scales by tracking the response of the superconducting state to finite pairing momentum. This approach allows the coherence length, penetration depth, and depairing current to be extracted on equal footing within a unified formalism.

Applying this framework to conventional superconductors, we obtain quantitative agreement with experimentally measured length scales across elemental, A15, and hydride materials using superconducting density functional theory [1]. Turning to strongly correlated superconductivity in alkali-doped fullerides (A$_3$C$_{60}$), dynamical mean-field theory reveals a regime in which strong correlations and multiorbital physics stabilize a local-pair superconducting state with elevated transition temperatures and robust phase stiffness despite short coherence lengths [2].

[1] M. Kawamura et al., arXiv:2603.05123
[2] N. Witt et al., npj Quantum Materials 9, 100 (2024); doi:10.1038/s41535-024-00706-7