The thermal quasiparticles in a clean type-II superconductor with line nodes give rise to a quadratic low-temperature change of the penetration depth, Δλ∼T2, as first shown by Kosztin and Leggett [I. Kosztin and A. J. Leggett, Phys. Rev. Lett. 79, 135 (1997)]. Here, we generalize this result to multiple nodes and compare it to numerically exact evaluations of the temperature-dependent penetration depth in Sr2RuO4 using a high-precision tight-binding model. We compare the calculations to recent penetration depth measurements in high purity single crystals of Sr2RuO4 [J. F. Landaeta et al., arXiv:2312.05129]. When assuming the order parameter to have B1g symmetry, we find that both a simple dx2−y2-wave and complicated gap structures with contributions from higher harmonics and accidental nodes can accommodate the experimental data.
@article{arxiv.2404.19365,
title = {Nonlocal electrodynamics and the penetration depth of superconducting Sr$_2$RuO$_4$},
author = {Henrik S. Røising and Andreas Kreisel and Brian M. Andersen},
journal= {arXiv preprint arXiv:2404.19365},
year = {2024}
}