SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 62: Ultrafast Dynamics of Light-Driven Systems

TT 62.4: Vortrag

Freitag, 31. März 2023, 10:15–10:30, HSZ 03

Influence of impurities on the Higgs mode in non-centrosymmetric superconductors — •Simon Klein and Dirk Manske — Max-Planck Institut für Festkörperforschung, Stuttgart, Deutschland

Recent interest for collective amplitude (Higgs) excitations focused on third harmonic generation (THG) experiments in single- and multi-band superconductors, both for singlet s- and d-wave gap structure. A resonance in the THG intensity appears, when matching the driving frequency to the energy of the corresponding investigated mode, leading to a phase jump at the resonance frequency. We extend these studies to superconductors without an inversion symmetry, which can be effectively described by a two-band model with an order parameter, consisting of spin singlet (even parity) and spin triplet (odd parity) components. We calculate the THG response, showing that it contains contributions from three distinguishable sources, namely the Higgs mode, the Leggett mode and quasiparticles. In the clean limit the quasiparticle contributions dominate the collective modes for all singlet-triplet ratios of the gap structure. By including already a small amount of impurities in the system, we find a significant enhancement of the Higgs mode contributions to the THG signal. Furthermore, we notice a significant change in the phase jump, which helps to differentiate between clean and dirty superconductors.