Effects of Nonmagnetic Impurities on Nonequilibrium Phase Transitions in Microwave-Driven Superconductors
Abstract
We investigate the nonequilibrium steady states of a microwave-driven BCS superconductor in the presence of nonmagnetic impurity scattering and energy relaxation. Using the Floquet-Nambu-Keldysh Green's function method together with the self-consistent Born approximation, we self-consistently determine the superconducting order parameter in the microwave-driven steady state. We find that the nonequilibrium phase diagram depends strongly on the impurity-scattering strength. When impurity scattering is absent or weak, the steady-state order parameter is single-valued at each temperature and drive frequency. At intermediate scattering strengths, we find bistability between microwave-enhanced and microwave-suppressed superconducting states. As the impurity-scattering strength increases further, we instead find bistability between the superconducting and normal states. This evolution reflects competition between two effects of microwave driving: Eliashberg-type enhancement through the redistribution of thermally excited quasiparticles and suppression through pair-breaking-induced quasiparticle generation. In contrast to the robustness of equilibrium s-wave superconductivity against nonmagnetic impurity scattering, our results demonstrate that nonmagnetic impurity scattering plays a central role in determining the character of nonequilibrium superconducting phase transitions under microwave driving.
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BibTeX
@misc{kawamura2026effects,
title = {{Effects of Nonmagnetic Impurities on Nonequilibrium Phase Transitions in Microwave-Driven Superconductors}},
author = {Taira Kawamura},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.25859},
eprint = {2610.25859},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.25859},
}
RIS
TY - UNPB
TI - Effects of Nonmagnetic Impurities on Nonequilibrium Phase Transitions in Microwave-Driven Superconductors
AU - Taira Kawamura
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.25859
UR - https://arxiv.org/abs/2610.25859
AB - We investigate the nonequilibrium steady states of a microwave-driven BCS superconductor in the presence of nonmagnetic impurity scattering and energy relaxation. Using the Floquet-Nambu-Keldysh Green's function method together with the self-consistent Born approximation, we self-consistently determine the superconducting order parameter in the microwave-driven steady state. We find that the nonequilibrium phase diagram depends strongly on the impurity-scattering strength. When impurity scattering is absent or weak, the steady-state order parameter is single-valued at each temperature and drive frequency. At intermediate scattering strengths, we find bistability between microwave-enhanced and microwave-suppressed superconducting states. As the impurity-scattering strength increases further, we instead find bistability between the superconducting and normal states. This evolution reflects competition between two effects of microwave driving: Eliashberg-type enhancement through the redistribution of thermally excited quasiparticles and suppression through pair-breaking-induced quasiparticle generation. In contrast to the robustness of equilibrium s-wave superconductivity against nonmagnetic impurity scattering, our results demonstrate that nonmagnetic impurity scattering plays a central role in determining the character of nonequilibrium superconducting phase transitions under microwave driving.
ER -