Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 22: Unconventional Superconductors

TT 22.10: Vortrag

Mittwoch, 7. September 2022, 18:00–18:15, H10

Collective Modes Contributions in Third-Harmonic Generation in Non-centrosymmetric Superconductors — •Simon Klein, Matteo Puviani, and Dirk Manske — Max Planck Institute for Solid State Research, Stuttgart, Germany

Recent interest for collective amplitude (Higgs) and phase (Leggett) excitations in single- and multi-band superconductors have led to various studies focused on third-harmonic generation (THG) experiments, 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 signal for the non-centrosymmetric compound CePt3Si, showing that it contains contributions from three distinguishable sources, namely the Higgs mode, the Leggett mode and quasiparticles. In the clean limit, only diamagnetic Raman-like processes contribute to the THG signal, whereas the quasiparticle contributions dominate the collective modes for all singlet-triplet ratios of the gap structure. In the dirty limit, we find a significant enhancement of the Higgs mode contributions to the THG signal, due to the inclusion of non-vanishing paramagnetic diagrams. We notice a significant change in the phase jump, which helps to differentiate between diamagnetic and paramagnetic results and thus between clean and dirty superconductors.