Revealing THz optical signatures of Shiba-state-induced gapped and gapless superconductivity
Revealing THz optical signatures of Shiba-state-induced gapped and gapless superconductivity
Understanding the interplay of superconductivity and magnetic disorder has been a long-standing challenge. Here we report a fully self-consistent calculation of the complex renormalization by exchange interactions and hence the complete phase diagram of conventional $s$-wave superconductors with magnetic impurities as well as the related physical properties including the optical response. We show that a small amount of magnetic disorder can drive the system into a gapless superconducting state, where the single-particle excitation gap vanishes whereas the superconducting order parameter $Î_0$ remains finite. In this phase, the linear optical conductivity exhibits a finite absorption over the low-frequency regime, particularly for photon energies below the conventional threshold $2|Î_0|$, even at low temperatures, in sharp contrast to the gapped state. The nonlinear response, however, remains coherent and is dominated by the Higgs-mode dynamics rather than gapless quasiparticle background. These findings reveal a fundamental distinction between dissipative single-particle excitations and coherent collective dynamics of the condensate, a feature likely general to other gapless superconductors, and introduces a fundamentally different detection scheme, using THz spectroscopy to probe the signatures of Shiba states.
F. Yang、R. Y. Fang、S. L. Zhang、L. Q. Chen
物理学光电子技术
F. Yang,R. Y. Fang,S. L. Zhang,L. Q. Chen.Revealing THz optical signatures of Shiba-state-induced gapped and gapless superconductivity[EB/OL].(2025-07-07)[2025-07-23].https://arxiv.org/abs/2507.05516.点此复制
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