We investigate the impact of two-level systems (TLSs) on superconductivity, treating them as soft modes localised in real space. We show that these defects can either enhance or suppress the superconducting critical temperature, depending on their surface density and average frequency. Using thin-film aluminium as a case study, we quantitatively describe how TLSs modify both the critical temperature and the zero-temperature superconducting gap. Our results thus highlight new opportunities for tailoring material properties through TLS engineering.
@article{arxiv.2510.23710,
title = {Tailoring Superconductivity with Two-Level Systems},
author = {Joshuah T. Heath and Alexander C. Tyner and S. Pamir Alpay and Peter Krogstrup and Alexander V. Balatsky},
journal= {arXiv preprint arXiv:2510.23710},
year = {2025}
}