Regensburg 2025 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 34: Superconductivity: Theory

TT 34.4: Vortrag

Mittwoch, 19. März 2025, 15:45–16:00, H36

Superconducting modes in the presence of Coulomb repulsion — •Joshua Althüser and Götz Uhrig — TU Dortmund, Otto-Hahn-Str. 4, 44227 Dortmund, Deutschland

We numerically study the collective excitations present in BCS-superconductors including screened Coulomb interactions. By varying the screening strength, we analyze its impact on the system. We use a formulation of the effective phonon-mediated interaction between electrons that depends on the energy transfer between particles, rather than being a constant in a small energy shell around the Fermi edge. We compute the system's Green's functions using the iterated equations of motion (iEoM) approach, which ultimately enables a comprehensive analysis of collective excitations. For weak couplings, we identify the well-known amplitude (Higgs) mode at the quasiparticle continuum's lower edge and the phase (Anderson-Bogoliubov) mode at zero energy for a neutral system, which shifts to higher energies as the Coulomb interactions are switched on. As the phononic coupling is increased, the Higgs mode emerges from the continuum, and additional phase and amplitude modes appear, persisting even with active Coulomb interactions.

Keywords: Collective excitations; Coulomb repulsion