We have investigated the normal and superconducting states of the technologically important compound Nb3Sn using 93Nb nuclear magnetic resonance. From spin-lattice relaxation we find strong suppression of the zero-temperature superconducting order parameter by magnetic field. Additionally we have identified an anomalously large electron-nuclear exchange interaction from spin-spin relaxation measurements, an order of magnitude beyond that of the nuclear dipolar coupling. This RKKY interaction evolves from normal to superconducting states, becoming essentially Lorentzian in the low temperature limit.
@article{arxiv.2502.00566,
title = {Nuclear spin coherence in superconducting Nb$_3$Sn},
author = {Gan Zhai and William P. Halperin and Arneil P. Reyes and Sam Posen and Chiara Tarantini and Manish Mandal and David C. Larbalestier},
journal= {arXiv preprint arXiv:2502.00566},
year = {2025}
}